qcodes.instrument

class qcodes.instrument.ChannelList(parent: InstrumentBase, name: str, chan_type: Type[InstrumentModuleType], chan_list: Optional[Sequence[InstrumentModuleType]] = None, snapshotable: bool = True, multichan_paramclass: Optional[Type[MultiChannelInstrumentParameter]] = None)

Bases: ChannelTuple, MutableSequence[InstrumentModuleType]

Mutable Container for channelized parameters that allows for sweeps over all channels, as well as addressing of individual channels.

This behaves like a python list i.e. it implements the collections.abc.MutableSequence interface.

Note it may be useful to use the mutable ChannelList while constructing it. E.g. adding channels as they are created, but in most use cases it is recommended to convert this to a ChannelTuple before adding it to an instrument. This can be done using the to_channel_tuple() method.

Parameters

• parent – The instrument to which this ChannelList should be attached.

• name – The name of the ChannelList.

• chan_type – The type of channel contained within this list.

• chan_list – An optional iterable of channels of type chan_type. This will create a list and immediately lock the ChannelList.

• snapshotable – Optionally disables taking of snapshots for a given ChannelList. This is used when objects stored inside a ChannelList are accessible in multiple ways and should not be repeated in an instrument snapshot.

• multichan_paramclass – The class of the object to be returned by the __getattr__() method of ChannelList. Should be a subclass of MultiChannelInstrumentParameter. Defaults to MultiChannelInstrumentParameter if None.

Raises

• ValueError – If chan_type is not a subclass of InstrumentChannel

• ValueError – If multichan_paramclass is not a subclass of MultiChannelInstrumentParameter (note that a class is a subclass of itself).

append(obj: InstrumentModuleType) → None

Append a Channel to this list. Requires that the ChannelList is not locked and that the channel is of the same type as the ones in the list.

Parameters

obj – New channel to add to the list.

clear() → None

Clear all items from the ChannelList.

remove(obj: InstrumentModuleType) → None

Removes obj from ChannelList if not locked.

Parameters

obj – Channel to remove from the list.

extend(objects: Iterable[InstrumentModuleType]) → None

Insert an iterable of objects into the list of channels.

Parameters

objects – A list of objects to add into the ChannelList.

insert(index: int, obj: InstrumentModuleType) → None

Insert an object into the ChannelList at a specific index.

Parameters

• index – Index to insert object.

• obj – Object of type chan_type to insert.

get_validator() → ChannelTupleValidator

Returns a validator that checks that the returned object is a channel in this ChannelList.

Raises

AttributeError – If the ChannelList is not locked.

lock() → None

Lock the channel list. Once this is done, the ChannelList is locked and any future changes to the list are prevented. Note this is not recommended and may be deprecated in the future. Use to_channel_tuple to convert this into a tuple instead.

to_channel_tuple() → ChannelTuple

Returns a ChannelTuple build from this ChannelList containing the same channels but without the ability to be modified.

__add__(other: ChannelTuple) → T

Return a new ChannelTuple containing the channels from both ChannelTuple self and r.

Both ChannelTuple must hold the same type and have the same parent.

Parameters

other – Right argument to add.

__getattr__(name: str) → Union[MultiChannelInstrumentParameter, Callable[[...], None], InstrumentModuleType]

Look up an attribute by name. If this is the name of a parameter or a function on the channel type contained in this container return a multi-channel function or parameter that can be used to get or set all items in a channel list simultaneously. If this is the name of a channel, return that channel.

Parameters

name – The name of the parameter, function or channel that we want to operate on.

__getitem__(i: Union[int, slice, Tuple[int, ...]]) → Union[InstrumentModuleType, T]

Return either a single channel, or a new ChannelTuple containing only the specified channels

Parameters

i – Either a single channel index or a slice of channels to get

count(obj: InstrumentModuleType) → int

Returns number of instances of the given object in the list

Parameters

obj – The object to find in the ChannelTuple.

get_channel_by_name(*names: str) → Union[InstrumentModuleType, T]

Get a channel by name, or a ChannelTuple if multiple names are given.

Parameters

*names – channel names

index(obj: InstrumentModuleType, start: int = 0, stop: int = 9223372036854775807) → int

Return the index of the given object

Parameters

• obj – The object to find in the channel list.

• start – Index to start searching from.

• stop – Index to stop searching at.

invalidate_cache() → None

Invalidate the cache of all parameters on the ChannelTuple.

load_metadata(metadata: Mapping[str, Any]) → None

Load metadata into this classes metadata dictionary.

Parameters

metadata – Metadata to load.

pop([index]) → item -- remove and return item at index (default last).

Raise IndexError if list is empty or index is out of range.

print_readable_snapshot(update: bool = False, max_chars: int = 80) → None

reverse()

S.reverse() – reverse IN PLACE

snapshot(update: Optional[bool] = False) → Dict[Any, Any]

Decorate a snapshot dictionary with metadata. DO NOT override this method if you want metadata in the snapshot instead, override snapshot_base().

Parameters

update – Passed to snapshot_base.

Returns

Base snapshot.

snapshot_base(update: Optional[bool] = True, params_to_skip_update: Optional[Sequence[str]] = None) → Dict[Any, Any]

State of the instrument as a JSON-compatible dict (everything that the custom JSON encoder class NumpyJSONEncoder supports).

Parameters

• update – If True, update the state by querying the instrument. If None only update if the state is known to be invalid. If False, just use the latest values in memory and never update.

• params_to_skip_update – List of parameter names that will be skipped in update even if update is True. This is useful if you have parameters that are slow to update but can be updated in a different way (as in the qdac). If you want to skip the update of certain parameters in all snapshots, use the snapshot_get attribute of those parameters instead.

Returns

base snapshot

Return type

dict

class qcodes.instrument.ChannelTuple(parent: InstrumentBase, name: str, chan_type: Type[InstrumentModuleType], chan_list: Optional[Sequence[InstrumentModuleType]] = None, snapshotable: bool = True, multichan_paramclass: Optional[Type[MultiChannelInstrumentParameter]] = None)

Bases: Metadatable, Sequence[InstrumentModuleType]

Container for channelized parameters that allows for sweeps over all channels, as well as addressing of individual channels.

This behaves like a python tuple i.e. it implements the collections.abc.Sequence interface.

Parameters

• parent – The instrument to which this ChannelTuple should be attached.

• name – The name of the ChannelTuple.

• chan_type – The type of channel contained within this tuple.

• chan_list – An optional iterable of channels of type chan_type.

• snapshotable – Optionally disables taking of snapshots for a given ChannelTuple. This is used when objects stored inside a ChannelTuple are accessible in multiple ways and should not be repeated in an instrument snapshot.

• multichan_paramclass – The class of the object to be returned by the __getattr__() method of ChannelTuple. Should be a subclass of MultiChannelInstrumentParameter. Defaults to MultiChannelInstrumentParameter if None.

Raises

• ValueError – If chan_type is not a subclass of InstrumentChannel

• ValueError – If multichan_paramclass is not a subclass of MultiChannelInstrumentParameter (note that a class is a subclass of itself).

__getitem__(i: int) → InstrumentModuleType

__getitem__(i: Union[slice, Tuple[int, ...]]) → T

Return either a single channel, or a new ChannelTuple containing only the specified channels

Parameters

i – Either a single channel index or a slice of channels to get

__add__(other: ChannelTuple) → T

Return a new ChannelTuple containing the channels from both ChannelTuple self and r.

Both ChannelTuple must hold the same type and have the same parent.

Parameters

other – Right argument to add.

index(obj: InstrumentModuleType, start: int = 0, stop: int = 9223372036854775807) → int

Return the index of the given object

Parameters

• obj – The object to find in the channel list.

• start – Index to start searching from.

• stop – Index to stop searching at.

count(obj: InstrumentModuleType) → int

Returns number of instances of the given object in the list

Parameters

obj – The object to find in the ChannelTuple.

get_channel_by_name(*names: str) → Union[InstrumentModuleType, T]

Get a channel by name, or a ChannelTuple if multiple names are given.

Parameters

*names – channel names

get_validator() → ChannelTupleValidator

Returns a validator that checks that the returned object is a channel in this ChannelTuple

snapshot_base(update: Optional[bool] = True, params_to_skip_update: Optional[Sequence[str]] = None) → Dict[Any, Any]

State of the instrument as a JSON-compatible dict (everything that the custom JSON encoder class NumpyJSONEncoder supports).

Parameters

• update – If True, update the state by querying the instrument. If None only update if the state is known to be invalid. If False, just use the latest values in memory and never update.

• params_to_skip_update – List of parameter names that will be skipped in update even if update is True. This is useful if you have parameters that are slow to update but can be updated in a different way (as in the qdac). If you want to skip the update of certain parameters in all snapshots, use the snapshot_get attribute of those parameters instead.

Returns

base snapshot

Return type

dict

__getattr__(name: str) → Union[MultiChannelInstrumentParameter, Callable[[...], None], InstrumentModuleType]

Look up an attribute by name. If this is the name of a parameter or a function on the channel type contained in this container return a multi-channel function or parameter that can be used to get or set all items in a channel list simultaneously. If this is the name of a channel, return that channel.

Parameters

name – The name of the parameter, function or channel that we want to operate on.

print_readable_snapshot(update: bool = False, max_chars: int = 80) → None

invalidate_cache() → None

Invalidate the cache of all parameters on the ChannelTuple.

load_metadata(metadata: Mapping[str, Any]) → None

Load metadata into this classes metadata dictionary.

Parameters

metadata – Metadata to load.

snapshot(update: Optional[bool] = False) → Dict[Any, Any]

Decorate a snapshot dictionary with metadata. DO NOT override this method if you want metadata in the snapshot instead, override snapshot_base().

Parameters

update – Passed to snapshot_base.

Returns

Base snapshot.

class qcodes.instrument.IPInstrument(*args: Any, **kwargs: Any)

Bases: Instrument

Bare socket ethernet instrument implementation. Use of VisaInstrument is promoted instead of this.

Parameters

• name – What this instrument is called locally.

• address – The IP address or name. If not given on construction, must be provided before any communication.

• port – The IP port. If not given on construction, must be provided before any communication.

• timeout – Seconds to allow for responses. Default 5.

• terminator – Character(s) to terminate each send. Default ‘n’.

• persistent – Whether to leave the socket open between calls. Default True.

• write_confirmation – Whether the instrument acknowledges writes with some response we should read. Default True.

• kwargs – additional static metadata to add to this instrument’s JSON snapshot.

See help for qcodes.Instrument for additional information on writing instrument subclasses.

set_address(address: Optional[str] = None, port: Optional[int] = None) → None

Change the IP address and/or port of this instrument.

Parameters

• address – The IP address or name.

• port – The IP port.

set_persistent(persistent: bool) → None

Change whether this instrument keeps its socket open between calls.

Parameters

persistent – Set True to keep the socket open all the time.

flush_connection() → None

set_timeout(timeout: float) → None

Change the read timeout for the socket.

Parameters

timeout – Seconds to allow for responses.

set_terminator(terminator: str) → None

Change the write terminator to use.

Parameters

terminator – Character(s) to terminate each send. Default ‘n’.

close() → None

Disconnect and irreversibly tear down the instrument.

write_raw(cmd: str) → None

Low-level interface to send a command that gets no response.

Parameters

cmd – The command to send to the instrument.

ask_raw(cmd: str) → str

Low-level interface to send a command an read a response.

Parameters

cmd – The command to send to the instrument.

Returns

The instrument’s string response.

snapshot_base(update: Optional[bool] = False, params_to_skip_update: Optional[Sequence[str]] = None) → Dict[Any, Any]

State of the instrument as a JSON-compatible dict (everything that the custom JSON encoder class NumpyJSONEncoder supports).

Parameters

• update – If True, update the state by querying the instrument. If None only update if the state is known to be invalid. If False, just use the latest values in memory and never update.

• params_to_skip_update – List of parameter names that will be skipped in update even if update is True. This is useful if you have parameters that are slow to update but can be updated in a different way (as in the qdac). If you want to skip the update of certain parameters in all snapshots, use the snapshot_get attribute of those parameters: instead.

Returns

base snapshot

Return type

dict

__del__() → None

Close the instrument and remove its instance record.

__getitem__(key: str) → Union[Callable[[...], Any], Parameter]

Delegate instrument[‘name’] to parameter or function ‘name’.

__getstate__() → None

Prevent pickling instruments, and give a nice error message.

__repr__() → str

Simplified repr giving just the class and name.

add_function(name: str, **kwargs: Any) → None

Bind one Function to this instrument.

Instrument subclasses can call this repeatedly in their __init__ for every real function of the instrument.

This functionality is meant for simple cases, principally things that map to simple commands like *RST (reset) or those with just a few arguments. It requires a fixed argument count, and positional args only. If your case is more complicated, you’re probably better off simply making a new method in your Instrument subclass definition.

Parameters

• name – How the Function will be stored within instrument.Functions and also how you address it using the shortcut methods: instrument.call(func_name, *args) etc.

• **kwargs – constructor kwargs for Function

Raises

KeyError – If this instrument already has a function with this name.

add_parameter(name: str, parameter_class: Optional[Type[ParameterBase]] = None, **kwargs: Any) → None

Bind one Parameter to this instrument.

Instrument subclasses can call this repeatedly in their __init__ for every real parameter of the instrument.

In this sense, parameters are the state variables of the instrument, anything the user can set and/or get.

Parameters

• name – How the parameter will be stored within parameters and also how you address it using the shortcut methods: instrument.set(param_name, value) etc.

• parameter_class – You can construct the parameter out of any class. Default parameters.Parameter.

• **kwargs – Constructor arguments for parameter_class.

Raises

• KeyError – If this instrument already has a parameter with this name and the parameter being replaced is not an abstract parameter.

• ValueError – If there is an existing abstract parameter and the unit of the new parameter is inconsistent with the existing one.

add_submodule(name: str, submodule: Union[InstrumentModule, ChannelTuple]) → None

Bind one submodule to this instrument.

Instrument subclasses can call this repeatedly in their __init__ method for every submodule of the instrument.

Submodules can effectively be considered as instruments within the main instrument, and should at minimum be snapshottable. For example, they can be used to either store logical groupings of parameters, which may or may not be repeated, or channel lists. They should either be an instance of an InstrumentModule or a ChannelTuple.

Parameters

• name – How the submodule will be stored within instrument.submodules and also how it can be addressed.

• submodule – The submodule to be stored.

Raises

• KeyError – If this instrument already contains a submodule with this name.

• TypeError – If the submodule that we are trying to add is not an instance of an Metadatable object.

property ancestors: List[qcodes.instrument.instrument_base.InstrumentBase]

Returns a list of instruments, starting from the current instrument and following to the parent instrument and the parents parent instrument until the root instrument is reached.

ask(cmd: str) → str

Write a command string to the hardware and return a response.

Subclasses that transform cmd should override this method, and in it call super().ask(new_cmd). Subclasses that define a new hardware communication should instead override ask_raw.

Parameters

cmd – The string to send to the instrument.

Returns

response

Raises

Exception – Wraps any underlying exception with extra context, including the command and the instrument.

call(func_name: str, *args: Any) → Any

Shortcut for calling a function from its name.

Parameters

• func_name – The name of a function of this instrument.

• *args – any arguments to the function.

Returns

The return value of the function.

classmethod close_all() → None

Try to close all instruments registered in _all_instruments This is handy for use with atexit to ensure that all instruments are closed when a python session is closed.

Examples

>>> atexit.register(qc.Instrument.close_all())

connect_message(idn_param: str = 'IDN', begin_time: Optional[float] = None) → None

Print a standard message on initial connection to an instrument.

Parameters

• idn_param – Name of parameter that returns ID dict. Default IDN.

• begin_time – time.time() when init started. Default is self._t0, set at start of Instrument.__init__.

delegate_attr_dicts: List[str] = ['parameters', 'functions', 'submodules']

A list of names (strings) of dictionaries which are (or will be) attributes of self, whose keys should be treated as attributes of self.

delegate_attr_objects: List[str] = []

A list of names (strings) of objects which are (or will be) attributes of self, whose attributes should be passed through to self.

static exist(name: str, instrument_class: Optional[type] = None) → bool

Check if an instrument with a given names exists (i.e. is already instantiated).

Parameters

• name – Name of the instrument.

• instrument_class – The type of instrument you are looking for.

classmethod find_instrument(name: str, instrument_class: Optional[Type[T]] = None) → T

Find an existing instrument by name.

Parameters

• name – Name of the instrument.

• instrument_class – The type of instrument you are looking for.

Returns

The instrument found.

Raises

• KeyError – If no instrument of that name was found, or if its reference is invalid (dead).

• TypeError – If a specific class was requested but a different type was found.

property full_name: str

get(param_name: str) → Any

Shortcut for getting a parameter from its name.

Parameters

param_name – The name of a parameter of this instrument.

Returns

The current value of the parameter.

get_idn() → Dict[str, Optional[str]]

Parse a standard VISA *IDN? response into an ID dict.

Even though this is the VISA standard, it applies to various other types as well, such as IPInstruments, so it is included here in the Instrument base class.

Override this if your instrument does not support *IDN? or returns a nonstandard IDN string. This string is supposed to be a comma-separated list of vendor, model, serial, and firmware, but semicolon and colon are also common separators so we accept them here as well.

Returns

A dict containing vendor, model, serial, and firmware.

classmethod instances() → List[Instrument]

Get all currently defined instances of this instrument class.

You can use this to get the objects back if you lose track of them, and it’s also used by the test system to find objects to test against.

Returns

A list of instances.

invalidate_cache() → None

Invalidate the cache of all parameters on the instrument. Calling this method will recursively mark the cache of all parameters on the instrument and any parameter on instrument modules as invalid.

This is useful if you have performed manual operations (e.g. using the frontpanel) which changes the state of the instrument outside QCoDeS.

This in turn means that the next snapshot of the instrument will trigger a (potentially slow) reread of all parameters of the instrument if you pass update=None to snapshot.

static is_valid(instr_instance: Instrument) → bool

Check if a given instance of an instrument is valid: if an instrument has been closed, its instance is not longer a “valid” instrument.

Parameters

instr_instance – Instance of an Instrument class or its subclass.

load_metadata(metadata: Mapping[str, Any]) → None

Load metadata into this classes metadata dictionary.

Parameters

metadata – Metadata to load.

property name: str

Name of the instrument This is equivalent to full_name for backwards compatibility.

property name_parts: List[str]

omit_delegate_attrs: List[str] = []

A list of attribute names (strings) to not delegate to any other dictionary or object.

property parent: Optional[qcodes.instrument.instrument_base.InstrumentBase]

Returns the parent instrument. By default this is None. Any SubInstrument should subclass this to return the parent instrument.

print_readable_snapshot(update: bool = False, max_chars: int = 80) → None

Prints a readable version of the snapshot. The readable snapshot includes the name, value and unit of each parameter. A convenience function to quickly get an overview of the status of an instrument.

Parameters

• update – If True, update the state by querying the instrument. If False, just use the latest values in memory. This argument gets passed to the snapshot function.

• max_chars – the maximum number of characters per line. The readable snapshot will be cropped if this value is exceeded. Defaults to 80 to be consistent with default terminal width.

classmethod record_instance(instance: Instrument) → None

Record (a weak ref to) an instance in a class’s instance list.

Also records the instance in list of all instruments, and verifies that there are no other instruments with the same name.

This method is called after initialization of the instrument is completed.

Parameters

instance – Instance to record.

Raises

KeyError – If another instance with the same name is already present.

classmethod remove_instance(instance: Instrument) → None

Remove a particular instance from the record.

Parameters

instance – The instance to remove

property root_instrument: qcodes.instrument.instrument_base.InstrumentBase

set(param_name: str, value: Any) → None

Shortcut for setting a parameter from its name and new value.

Parameters

• param_name – The name of a parameter of this instrument.

• value – The new value to set.

shared_kwargs = ()

property short_name: str

Short name of the instrument

snapshot(update: Optional[bool] = False) → Dict[Any, Any]

Decorate a snapshot dictionary with metadata. DO NOT override this method if you want metadata in the snapshot instead, override snapshot_base().

Parameters

update – Passed to snapshot_base.

Returns

Base snapshot.

validate_status(verbose: bool = False) → None

Validate the values of all gettable parameters

The validation is done for all parameters that have both a get and set method.

Parameters

verbose – If True, then information about the parameters that are being check is printed.

write(cmd: str) → None

Write a command string with NO response to the hardware.

Subclasses that transform cmd should override this method, and in it call super().write(new_cmd). Subclasses that define a new hardware communication should instead override write_raw.

Parameters

cmd – The string to send to the instrument.

Raises

Exception – Wraps any underlying exception with extra context, including the command and the instrument.

parameters: Dict[str, ParameterBase] = {}

All the parameters supported by this instrument. Usually populated via add_parameter().

functions: Dict[str, Function] = {}

All the functions supported by this instrument. Usually populated via add_function().

submodules: Dict[str, Union['InstrumentModule', 'ChannelTuple']] = {}

All the submodules of this instrument such as channel lists or logical groupings of parameters. Usually populated via add_submodule().

instrument_modules: Dict[str, 'InstrumentModule'] = {}

All the InstrumentModule of this instrument Usually populated via add_submodule().

class qcodes.instrument.Instrument(*args: Any, **kwargs: Any)

Bases: InstrumentBase

Base class for all QCodes instruments.

Parameters

• name – an identifier for this instrument, particularly for attaching it to a Station.

• metadata – additional static metadata to add to this instrument’s JSON snapshot.

shared_kwargs = ()

get_idn() → Dict[str, Optional[str]]

Parse a standard VISA *IDN? response into an ID dict.

Even though this is the VISA standard, it applies to various other types as well, such as IPInstruments, so it is included here in the Instrument base class.

Override this if your instrument does not support *IDN? or returns a nonstandard IDN string. This string is supposed to be a comma-separated list of vendor, model, serial, and firmware, but semicolon and colon are also common separators so we accept them here as well.

Returns

A dict containing vendor, model, serial, and firmware.

connect_message(idn_param: str = 'IDN', begin_time: Optional[float] = None) → None

Print a standard message on initial connection to an instrument.

Parameters

• idn_param – Name of parameter that returns ID dict. Default IDN.

• begin_time – time.time() when init started. Default is self._t0, set at start of Instrument.__init__.

__repr__() → str

Simplified repr giving just the class and name.

__del__() → None

Close the instrument and remove its instance record.

close() → None

Irreversibly stop this instrument and free its resources.

Subclasses should override this if they have other specific resources to close.

classmethod close_all() → None

Try to close all instruments registered in _all_instruments This is handy for use with atexit to ensure that all instruments are closed when a python session is closed.

Examples

>>> atexit.register(qc.Instrument.close_all())

classmethod record_instance(instance: Instrument) → None

Record (a weak ref to) an instance in a class’s instance list.

Also records the instance in list of all instruments, and verifies that there are no other instruments with the same name.

This method is called after initialization of the instrument is completed.

Parameters

instance – Instance to record.

Raises

KeyError – If another instance with the same name is already present.

classmethod instances() → List[Instrument]

Get all currently defined instances of this instrument class.

You can use this to get the objects back if you lose track of them, and it’s also used by the test system to find objects to test against.

Returns

A list of instances.

classmethod remove_instance(instance: Instrument) → None

Remove a particular instance from the record.

Parameters

instance – The instance to remove

classmethod find_instrument(name: str, instrument_class: Optional[Type[T]] = None) → T

Find an existing instrument by name.

Parameters

• name – Name of the instrument.

• instrument_class – The type of instrument you are looking for.

Returns

The instrument found.

Raises

• KeyError – If no instrument of that name was found, or if its reference is invalid (dead).

• TypeError – If a specific class was requested but a different type was found.

static exist(name: str, instrument_class: Optional[type] = None) → bool

Check if an instrument with a given names exists (i.e. is already instantiated).

Parameters

• name – Name of the instrument.

• instrument_class – The type of instrument you are looking for.

static is_valid(instr_instance: Instrument) → bool

Check if a given instance of an instrument is valid: if an instrument has been closed, its instance is not longer a “valid” instrument.

Parameters

instr_instance – Instance of an Instrument class or its subclass.

write(cmd: str) → None

Write a command string with NO response to the hardware.

Subclasses that transform cmd should override this method, and in it call super().write(new_cmd). Subclasses that define a new hardware communication should instead override write_raw.

Parameters

cmd – The string to send to the instrument.

Raises

Exception – Wraps any underlying exception with extra context, including the command and the instrument.

write_raw(cmd: str) → None

Low level method to write a command string to the hardware.

Subclasses that define a new hardware communication should override this method. Subclasses that transform cmd should instead override write.

Parameters

cmd – The string to send to the instrument.

ask(cmd: str) → str

Write a command string to the hardware and return a response.

Subclasses that transform cmd should override this method, and in it call super().ask(new_cmd). Subclasses that define a new hardware communication should instead override ask_raw.

Parameters

cmd – The string to send to the instrument.

Returns

response

Raises

Exception – Wraps any underlying exception with extra context, including the command and the instrument.

ask_raw(cmd: str) → str

Low level method to write to the hardware and return a response.

Subclasses that define a new hardware communication should override this method. Subclasses that transform cmd should instead override ask.

Parameters

cmd – The string to send to the instrument.

__getitem__(key: str) → Union[Callable[[...], Any], Parameter]

Delegate instrument[‘name’] to parameter or function ‘name’.

__getstate__() → None

Prevent pickling instruments, and give a nice error message.

add_function(name: str, **kwargs: Any) → None

Bind one Function to this instrument.

Instrument subclasses can call this repeatedly in their __init__ for every real function of the instrument.

This functionality is meant for simple cases, principally things that map to simple commands like *RST (reset) or those with just a few arguments. It requires a fixed argument count, and positional args only. If your case is more complicated, you’re probably better off simply making a new method in your Instrument subclass definition.

Parameters

• name – How the Function will be stored within instrument.Functions and also how you address it using the shortcut methods: instrument.call(func_name, *args) etc.

• **kwargs – constructor kwargs for Function

Raises

KeyError – If this instrument already has a function with this name.

add_parameter(name: str, parameter_class: Optional[Type[ParameterBase]] = None, **kwargs: Any) → None

Bind one Parameter to this instrument.

Instrument subclasses can call this repeatedly in their __init__ for every real parameter of the instrument.

In this sense, parameters are the state variables of the instrument, anything the user can set and/or get.

Parameters

• name – How the parameter will be stored within parameters and also how you address it using the shortcut methods: instrument.set(param_name, value) etc.

• parameter_class – You can construct the parameter out of any class. Default parameters.Parameter.

• **kwargs – Constructor arguments for parameter_class.

Raises

• KeyError – If this instrument already has a parameter with this name and the parameter being replaced is not an abstract parameter.

• ValueError – If there is an existing abstract parameter and the unit of the new parameter is inconsistent with the existing one.

add_submodule(name: str, submodule: Union[InstrumentModule, ChannelTuple]) → None

Bind one submodule to this instrument.

Instrument subclasses can call this repeatedly in their __init__ method for every submodule of the instrument.

Submodules can effectively be considered as instruments within the main instrument, and should at minimum be snapshottable. For example, they can be used to either store logical groupings of parameters, which may or may not be repeated, or channel lists. They should either be an instance of an InstrumentModule or a ChannelTuple.

Parameters

• name – How the submodule will be stored within instrument.submodules and also how it can be addressed.

• submodule – The submodule to be stored.

Raises

• KeyError – If this instrument already contains a submodule with this name.

• TypeError – If the submodule that we are trying to add is not an instance of an Metadatable object.

property ancestors: List[qcodes.instrument.instrument_base.InstrumentBase]

Returns a list of instruments, starting from the current instrument and following to the parent instrument and the parents parent instrument until the root instrument is reached.

call(func_name: str, *args: Any) → Any

Shortcut for calling a function from its name.

Parameters

• func_name – The name of a function of this instrument.

• *args – any arguments to the function.

Returns

The return value of the function.

delegate_attr_dicts: List[str] = ['parameters', 'functions', 'submodules']

A list of names (strings) of dictionaries which are (or will be) attributes of self, whose keys should be treated as attributes of self.

delegate_attr_objects: List[str] = []

A list of names (strings) of objects which are (or will be) attributes of self, whose attributes should be passed through to self.

property full_name: str

get(param_name: str) → Any

Shortcut for getting a parameter from its name.

Parameters

param_name – The name of a parameter of this instrument.

Returns

The current value of the parameter.

invalidate_cache() → None

Invalidate the cache of all parameters on the instrument. Calling this method will recursively mark the cache of all parameters on the instrument and any parameter on instrument modules as invalid.

This is useful if you have performed manual operations (e.g. using the frontpanel) which changes the state of the instrument outside QCoDeS.

This in turn means that the next snapshot of the instrument will trigger a (potentially slow) reread of all parameters of the instrument if you pass update=None to snapshot.

load_metadata(metadata: Mapping[str, Any]) → None

Load metadata into this classes metadata dictionary.

Parameters

metadata – Metadata to load.

property name: str

Name of the instrument This is equivalent to full_name for backwards compatibility.

property name_parts: List[str]

omit_delegate_attrs: List[str] = []

A list of attribute names (strings) to not delegate to any other dictionary or object.

property parent: Optional[qcodes.instrument.instrument_base.InstrumentBase]

Returns the parent instrument. By default this is None. Any SubInstrument should subclass this to return the parent instrument.

print_readable_snapshot(update: bool = False, max_chars: int = 80) → None

Prints a readable version of the snapshot. The readable snapshot includes the name, value and unit of each parameter. A convenience function to quickly get an overview of the status of an instrument.

Parameters

• update – If True, update the state by querying the instrument. If False, just use the latest values in memory. This argument gets passed to the snapshot function.

• max_chars – the maximum number of characters per line. The readable snapshot will be cropped if this value is exceeded. Defaults to 80 to be consistent with default terminal width.

property root_instrument: qcodes.instrument.instrument_base.InstrumentBase

set(param_name: str, value: Any) → None

Shortcut for setting a parameter from its name and new value.

Parameters

• param_name – The name of a parameter of this instrument.

• value – The new value to set.

property short_name: str

Short name of the instrument

snapshot(update: Optional[bool] = False) → Dict[Any, Any]

Decorate a snapshot dictionary with metadata. DO NOT override this method if you want metadata in the snapshot instead, override snapshot_base().

Parameters

update – Passed to snapshot_base.

Returns

Base snapshot.

snapshot_base(update: Optional[bool] = False, params_to_skip_update: Optional[Sequence[str]] = None) → Dict[Any, Any]

State of the instrument as a JSON-compatible dict (everything that the custom JSON encoder class NumpyJSONEncoder supports).

Parameters

• update – If True, update the state by querying the instrument. If None update the state if known to be invalid. If False, just use the latest values in memory and never update state.

• params_to_skip_update – List of parameter names that will be skipped in update even if update is True. This is useful if you have parameters that are slow to update but can be updated in a different way (as in the qdac). If you want to skip the update of certain parameters in all snapshots, use the snapshot_get attribute of those parameters instead.

Returns

base snapshot

Return type

dict

validate_status(verbose: bool = False) → None

Validate the values of all gettable parameters

The validation is done for all parameters that have both a get and set method.

Parameters

verbose – If True, then information about the parameters that are being check is printed.

parameters: Dict[str, ParameterBase] = {}

All the parameters supported by this instrument. Usually populated via add_parameter().

functions: Dict[str, Function] = {}

All the functions supported by this instrument. Usually populated via add_function().

submodules: Dict[str, Union['InstrumentModule', 'ChannelTuple']] = {}

All the submodules of this instrument such as channel lists or logical groupings of parameters. Usually populated via add_submodule().

instrument_modules: Dict[str, 'InstrumentModule'] = {}

All the InstrumentModule of this instrument Usually populated via add_submodule().

class qcodes.instrument.InstrumentBase(name: str, metadata: Optional[Mapping[Any, Any]] = None)

Bases: Metadatable, DelegateAttributes

Base class for all QCodes instruments and instrument channels

Parameters

• name – an identifier for this instrument, particularly for attaching it to a Station.

• metadata – additional static metadata to add to this instrument’s JSON snapshot.

parameters: Dict[str, ParameterBase] = {}

All the parameters supported by this instrument. Usually populated via add_parameter().

functions: Dict[str, Function] = {}

All the functions supported by this instrument. Usually populated via add_function().

submodules: Dict[str, Union['InstrumentModule', 'ChannelTuple']] = {}

All the submodules of this instrument such as channel lists or logical groupings of parameters. Usually populated via add_submodule().

instrument_modules: Dict[str, 'InstrumentModule'] = {}

All the InstrumentModule of this instrument Usually populated via add_submodule().

add_parameter(name: str, parameter_class: Optional[Type[ParameterBase]] = None, **kwargs: Any) → None

Bind one Parameter to this instrument.

Instrument subclasses can call this repeatedly in their __init__ for every real parameter of the instrument.

In this sense, parameters are the state variables of the instrument, anything the user can set and/or get.

Parameters

• name – How the parameter will be stored within parameters and also how you address it using the shortcut methods: instrument.set(param_name, value) etc.

• parameter_class – You can construct the parameter out of any class. Default parameters.Parameter.

• **kwargs – Constructor arguments for parameter_class.

Raises

• KeyError – If this instrument already has a parameter with this name and the parameter being replaced is not an abstract parameter.

• ValueError – If there is an existing abstract parameter and the unit of the new parameter is inconsistent with the existing one.

add_function(name: str, **kwargs: Any) → None

Bind one Function to this instrument.

Instrument subclasses can call this repeatedly in their __init__ for every real function of the instrument.

This functionality is meant for simple cases, principally things that map to simple commands like *RST (reset) or those with just a few arguments. It requires a fixed argument count, and positional args only. If your case is more complicated, you’re probably better off simply making a new method in your Instrument subclass definition.

Parameters

• name – How the Function will be stored within instrument.Functions and also how you address it using the shortcut methods: instrument.call(func_name, *args) etc.

• **kwargs – constructor kwargs for Function

Raises

KeyError – If this instrument already has a function with this name.

add_submodule(name: str, submodule: Union[InstrumentModule, ChannelTuple]) → None

Bind one submodule to this instrument.

Instrument subclasses can call this repeatedly in their __init__ method for every submodule of the instrument.

Submodules can effectively be considered as instruments within the main instrument, and should at minimum be snapshottable. For example, they can be used to either store logical groupings of parameters, which may or may not be repeated, or channel lists. They should either be an instance of an InstrumentModule or a ChannelTuple.

Parameters

• name – How the submodule will be stored within instrument.submodules and also how it can be addressed.

• submodule – The submodule to be stored.

Raises

• KeyError – If this instrument already contains a submodule with this name.

• TypeError – If the submodule that we are trying to add is not an instance of an Metadatable object.

snapshot_base(update: Optional[bool] = False, params_to_skip_update: Optional[Sequence[str]] = None) → Dict[Any, Any]

State of the instrument as a JSON-compatible dict (everything that the custom JSON encoder class NumpyJSONEncoder supports).

Parameters

• update – If True, update the state by querying the instrument. If None update the state if known to be invalid. If False, just use the latest values in memory and never update state.

• params_to_skip_update – List of parameter names that will be skipped in update even if update is True. This is useful if you have parameters that are slow to update but can be updated in a different way (as in the qdac). If you want to skip the update of certain parameters in all snapshots, use the snapshot_get attribute of those parameters instead.

Returns

base snapshot

Return type

dict

print_readable_snapshot(update: bool = False, max_chars: int = 80) → None

Prints a readable version of the snapshot. The readable snapshot includes the name, value and unit of each parameter. A convenience function to quickly get an overview of the status of an instrument.

Parameters

• update – If True, update the state by querying the instrument. If False, just use the latest values in memory. This argument gets passed to the snapshot function.

• max_chars – the maximum number of characters per line. The readable snapshot will be cropped if this value is exceeded. Defaults to 80 to be consistent with default terminal width.

invalidate_cache() → None

Invalidate the cache of all parameters on the instrument. Calling this method will recursively mark the cache of all parameters on the instrument and any parameter on instrument modules as invalid.

This is useful if you have performed manual operations (e.g. using the frontpanel) which changes the state of the instrument outside QCoDeS.

This in turn means that the next snapshot of the instrument will trigger a (potentially slow) reread of all parameters of the instrument if you pass update=None to snapshot.

property parent: Optional[qcodes.instrument.instrument_base.InstrumentBase]

Returns the parent instrument. By default this is None. Any SubInstrument should subclass this to return the parent instrument.

property ancestors: List[qcodes.instrument.instrument_base.InstrumentBase]

Returns a list of instruments, starting from the current instrument and following to the parent instrument and the parents parent instrument until the root instrument is reached.

property root_instrument: qcodes.instrument.instrument_base.InstrumentBase

property name_parts: List[str]

property full_name: str

property name: str

Name of the instrument This is equivalent to full_name for backwards compatibility.

property short_name: str

Short name of the instrument

delegate_attr_dicts: List[str] = ['parameters', 'functions', 'submodules']

A list of names (strings) of dictionaries which are (or will be) attributes of self, whose keys should be treated as attributes of self.

__getitem__(key: str) → Union[Callable[[...], Any], Parameter]

Delegate instrument[‘name’] to parameter or function ‘name’.

delegate_attr_objects: List[str] = []

A list of names (strings) of objects which are (or will be) attributes of self, whose attributes should be passed through to self.

load_metadata(metadata: Mapping[str, Any]) → None

Load metadata into this classes metadata dictionary.

Parameters

metadata – Metadata to load.

omit_delegate_attrs: List[str] = []

A list of attribute names (strings) to not delegate to any other dictionary or object.

set(param_name: str, value: Any) → None

Shortcut for setting a parameter from its name and new value.

Parameters

• param_name – The name of a parameter of this instrument.

• value – The new value to set.

snapshot(update: Optional[bool] = False) → Dict[Any, Any]

Decorate a snapshot dictionary with metadata. DO NOT override this method if you want metadata in the snapshot instead, override snapshot_base().

Parameters

update – Passed to snapshot_base.

Returns

Base snapshot.

get(param_name: str) → Any

Shortcut for getting a parameter from its name.

Parameters

param_name – The name of a parameter of this instrument.

Returns

The current value of the parameter.

call(func_name: str, *args: Any) → Any

Shortcut for calling a function from its name.

Parameters

• func_name – The name of a function of this instrument.

• *args – any arguments to the function.

Returns

The return value of the function.

__getstate__() → None

Prevent pickling instruments, and give a nice error message.

validate_status(verbose: bool = False) → None

Validate the values of all gettable parameters

The validation is done for all parameters that have both a get and set method.

Parameters

verbose – If True, then information about the parameters that are being check is printed.

class qcodes.instrument.InstrumentChannel(parent: InstrumentBase, name: str, **kwargs: Any)

Bases: InstrumentModule

__getitem__(key: str) → Union[Callable[[...], Any], Parameter]

Delegate instrument[‘name’] to parameter or function ‘name’.

__getstate__() → None

Prevent pickling instruments, and give a nice error message.

__repr__() → str

Custom repr to give parent information

add_function(name: str, **kwargs: Any) → None

Bind one Function to this instrument.

Instrument subclasses can call this repeatedly in their __init__ for every real function of the instrument.

This functionality is meant for simple cases, principally things that map to simple commands like *RST (reset) or those with just a few arguments. It requires a fixed argument count, and positional args only. If your case is more complicated, you’re probably better off simply making a new method in your Instrument subclass definition.

Parameters

• name – How the Function will be stored within instrument.Functions and also how you address it using the shortcut methods: instrument.call(func_name, *args) etc.

• **kwargs – constructor kwargs for Function

Raises

KeyError – If this instrument already has a function with this name.

add_parameter(name: str, parameter_class: Optional[Type[ParameterBase]] = None, **kwargs: Any) → None

Bind one Parameter to this instrument.

Instrument subclasses can call this repeatedly in their __init__ for every real parameter of the instrument.

In this sense, parameters are the state variables of the instrument, anything the user can set and/or get.

Parameters

• name – How the parameter will be stored within parameters and also how you address it using the shortcut methods: instrument.set(param_name, value) etc.

• parameter_class – You can construct the parameter out of any class. Default parameters.Parameter.

• **kwargs – Constructor arguments for parameter_class.

Raises

• KeyError – If this instrument already has a parameter with this name and the parameter being replaced is not an abstract parameter.

• ValueError – If there is an existing abstract parameter and the unit of the new parameter is inconsistent with the existing one.

add_submodule(name: str, submodule: Union[InstrumentModule, ChannelTuple]) → None

Bind one submodule to this instrument.

Instrument subclasses can call this repeatedly in their __init__ method for every submodule of the instrument.

Submodules can effectively be considered as instruments within the main instrument, and should at minimum be snapshottable. For example, they can be used to either store logical groupings of parameters, which may or may not be repeated, or channel lists. They should either be an instance of an InstrumentModule or a ChannelTuple.

Parameters

• name – How the submodule will be stored within instrument.submodules and also how it can be addressed.

• submodule – The submodule to be stored.

Raises

• KeyError – If this instrument already contains a submodule with this name.

• TypeError – If the submodule that we are trying to add is not an instance of an Metadatable object.

property ancestors: List[qcodes.instrument.instrument_base.InstrumentBase]

Returns a list of instruments, starting from the current instrument and following to the parent instrument and the parents parent instrument until the root instrument is reached.

ask(cmd: str) → str

ask_raw(cmd: str) → str

call(func_name: str, *args: Any) → Any

Shortcut for calling a function from its name.

Parameters

• func_name – The name of a function of this instrument.

• *args – any arguments to the function.

Returns

The return value of the function.

delegate_attr_dicts: List[str] = ['parameters', 'functions', 'submodules']

A list of names (strings) of dictionaries which are (or will be) attributes of self, whose keys should be treated as attributes of self.

delegate_attr_objects: List[str] = []

A list of names (strings) of objects which are (or will be) attributes of self, whose attributes should be passed through to self.

property full_name: str

get(param_name: str) → Any

Shortcut for getting a parameter from its name.

Parameters

param_name – The name of a parameter of this instrument.

Returns

The current value of the parameter.

invalidate_cache() → None

Invalidate the cache of all parameters on the instrument. Calling this method will recursively mark the cache of all parameters on the instrument and any parameter on instrument modules as invalid.

This is useful if you have performed manual operations (e.g. using the frontpanel) which changes the state of the instrument outside QCoDeS.

This in turn means that the next snapshot of the instrument will trigger a (potentially slow) reread of all parameters of the instrument if you pass update=None to snapshot.

load_metadata(metadata: Mapping[str, Any]) → None

Load metadata into this classes metadata dictionary.

Parameters

metadata – Metadata to load.

property name: str

Name of the instrument This is equivalent to full_name for backwards compatibility.

property name_parts: List[str]

omit_delegate_attrs: List[str] = []

A list of attribute names (strings) to not delegate to any other dictionary or object.

property parent: qcodes.instrument.instrument_base.InstrumentBase

Returns the parent instrument. By default this is None. Any SubInstrument should subclass this to return the parent instrument.

print_readable_snapshot(update: bool = False, max_chars: int = 80) → None

Prints a readable version of the snapshot. The readable snapshot includes the name, value and unit of each parameter. A convenience function to quickly get an overview of the status of an instrument.

Parameters

• update – If True, update the state by querying the instrument. If False, just use the latest values in memory. This argument gets passed to the snapshot function.

• max_chars – the maximum number of characters per line. The readable snapshot will be cropped if this value is exceeded. Defaults to 80 to be consistent with default terminal width.

property root_instrument: qcodes.instrument.instrument_base.InstrumentBase

set(param_name: str, value: Any) → None

Shortcut for setting a parameter from its name and new value.

Parameters

• param_name – The name of a parameter of this instrument.

• value – The new value to set.

property short_name: str

Short name of the instrument

snapshot(update: Optional[bool] = False) → Dict[Any, Any]

Decorate a snapshot dictionary with metadata. DO NOT override this method if you want metadata in the snapshot instead, override snapshot_base().

Parameters

update – Passed to snapshot_base.

Returns

Base snapshot.

snapshot_base(update: Optional[bool] = False, params_to_skip_update: Optional[Sequence[str]] = None) → Dict[Any, Any]

State of the instrument as a JSON-compatible dict (everything that the custom JSON encoder class NumpyJSONEncoder supports).

Parameters

• update – If True, update the state by querying the instrument. If None update the state if known to be invalid. If False, just use the latest values in memory and never update state.

• params_to_skip_update – List of parameter names that will be skipped in update even if update is True. This is useful if you have parameters that are slow to update but can be updated in a different way (as in the qdac). If you want to skip the update of certain parameters in all snapshots, use the snapshot_get attribute of those parameters instead.

Returns

base snapshot

Return type

dict

validate_status(verbose: bool = False) → None

Validate the values of all gettable parameters

The validation is done for all parameters that have both a get and set method.

Parameters

verbose – If True, then information about the parameters that are being check is printed.

write(cmd: str) → None

write_raw(cmd: str) → None

parameters: Dict[str, ParameterBase] = {}

All the parameters supported by this instrument. Usually populated via add_parameter().

functions: Dict[str, Function] = {}

All the functions supported by this instrument. Usually populated via add_function().

submodules: Dict[str, Union['InstrumentModule', 'ChannelTuple']] = {}

All the submodules of this instrument such as channel lists or logical groupings of parameters. Usually populated via add_submodule().

instrument_modules: Dict[str, 'InstrumentModule'] = {}

All the InstrumentModule of this instrument Usually populated via add_submodule().

metadata: Dict[str, Any] = {}

class qcodes.instrument.InstrumentModule(parent: InstrumentBase, name: str, **kwargs: Any)

Bases: InstrumentBase

Base class for a module in an instrument. This could be in the form of a channel (e.g. something that the instrument has multiple instances of) or another logical grouping of parameters that you wish to group together separate from the rest of the instrument.

Parameters

• parent – The instrument to which this module should be attached.

• name – The name of this module.

__repr__() → str

Custom repr to give parent information

write(cmd: str) → None

write_raw(cmd: str) → None

ask(cmd: str) → str

ask_raw(cmd: str) → str

property parent: qcodes.instrument.instrument_base.InstrumentBase

Returns the parent instrument. By default this is None. Any SubInstrument should subclass this to return the parent instrument.

property root_instrument: qcodes.instrument.instrument_base.InstrumentBase

property name_parts: List[str]

__getitem__(key: str) → Union[Callable[[...], Any], Parameter]

Delegate instrument[‘name’] to parameter or function ‘name’.

__getstate__() → None

Prevent pickling instruments, and give a nice error message.

add_function(name: str, **kwargs: Any) → None

Bind one Function to this instrument.

Instrument subclasses can call this repeatedly in their __init__ for every real function of the instrument.

This functionality is meant for simple cases, principally things that map to simple commands like *RST (reset) or those with just a few arguments. It requires a fixed argument count, and positional args only. If your case is more complicated, you’re probably better off simply making a new method in your Instrument subclass definition.

Parameters

• name – How the Function will be stored within instrument.Functions and also how you address it using the shortcut methods: instrument.call(func_name, *args) etc.

• **kwargs – constructor kwargs for Function

Raises

KeyError – If this instrument already has a function with this name.

add_parameter(name: str, parameter_class: Optional[Type[ParameterBase]] = None, **kwargs: Any) → None

Bind one Parameter to this instrument.

Instrument subclasses can call this repeatedly in their __init__ for every real parameter of the instrument.

In this sense, parameters are the state variables of the instrument, anything the user can set and/or get.

Parameters

• name – How the parameter will be stored within parameters and also how you address it using the shortcut methods: instrument.set(param_name, value) etc.

• parameter_class – You can construct the parameter out of any class. Default parameters.Parameter.

• **kwargs – Constructor arguments for parameter_class.

Raises

• KeyError – If this instrument already has a parameter with this name and the parameter being replaced is not an abstract parameter.

• ValueError – If there is an existing abstract parameter and the unit of the new parameter is inconsistent with the existing one.

add_submodule(name: str, submodule: Union[InstrumentModule, ChannelTuple]) → None

Bind one submodule to this instrument.

Instrument subclasses can call this repeatedly in their __init__ method for every submodule of the instrument.

Submodules can effectively be considered as instruments within the main instrument, and should at minimum be snapshottable. For example, they can be used to either store logical groupings of parameters, which may or may not be repeated, or channel lists. They should either be an instance of an InstrumentModule or a ChannelTuple.

Parameters

• name – How the submodule will be stored within instrument.submodules and also how it can be addressed.

• submodule – The submodule to be stored.

Raises

• KeyError – If this instrument already contains a submodule with this name.

• TypeError – If the submodule that we are trying to add is not an instance of an Metadatable object.

property ancestors: List[qcodes.instrument.instrument_base.InstrumentBase]

Returns a list of instruments, starting from the current instrument and following to the parent instrument and the parents parent instrument until the root instrument is reached.

call(func_name: str, *args: Any) → Any

Shortcut for calling a function from its name.

Parameters

• func_name – The name of a function of this instrument.

• *args – any arguments to the function.

Returns

The return value of the function.

delegate_attr_dicts: List[str] = ['parameters', 'functions', 'submodules']

A list of names (strings) of dictionaries which are (or will be) attributes of self, whose keys should be treated as attributes of self.

delegate_attr_objects: List[str] = []

A list of names (strings) of objects which are (or will be) attributes of self, whose attributes should be passed through to self.

property full_name: str

get(param_name: str) → Any

Shortcut for getting a parameter from its name.

Parameters

param_name – The name of a parameter of this instrument.

Returns

The current value of the parameter.

invalidate_cache() → None

Invalidate the cache of all parameters on the instrument. Calling this method will recursively mark the cache of all parameters on the instrument and any parameter on instrument modules as invalid.

This is useful if you have performed manual operations (e.g. using the frontpanel) which changes the state of the instrument outside QCoDeS.

This in turn means that the next snapshot of the instrument will trigger a (potentially slow) reread of all parameters of the instrument if you pass update=None to snapshot.

load_metadata(metadata: Mapping[str, Any]) → None

Load metadata into this classes metadata dictionary.

Parameters

metadata – Metadata to load.

property name: str

Name of the instrument This is equivalent to full_name for backwards compatibility.

omit_delegate_attrs: List[str] = []

A list of attribute names (strings) to not delegate to any other dictionary or object.

print_readable_snapshot(update: bool = False, max_chars: int = 80) → None

Prints a readable version of the snapshot. The readable snapshot includes the name, value and unit of each parameter. A convenience function to quickly get an overview of the status of an instrument.

Parameters

• update – If True, update the state by querying the instrument. If False, just use the latest values in memory. This argument gets passed to the snapshot function.

• max_chars – the maximum number of characters per line. The readable snapshot will be cropped if this value is exceeded. Defaults to 80 to be consistent with default terminal width.

set(param_name: str, value: Any) → None

Shortcut for setting a parameter from its name and new value.

Parameters

• param_name – The name of a parameter of this instrument.

• value – The new value to set.

property short_name: str

Short name of the instrument

snapshot(update: Optional[bool] = False) → Dict[Any, Any]

Decorate a snapshot dictionary with metadata. DO NOT override this method if you want metadata in the snapshot instead, override snapshot_base().

Parameters

update – Passed to snapshot_base.

Returns

Base snapshot.

snapshot_base(update: Optional[bool] = False, params_to_skip_update: Optional[Sequence[str]] = None) → Dict[Any, Any]

State of the instrument as a JSON-compatible dict (everything that the custom JSON encoder class NumpyJSONEncoder supports).

Parameters

• update – If True, update the state by querying the instrument. If None update the state if known to be invalid. If False, just use the latest values in memory and never update state.

• params_to_skip_update – List of parameter names that will be skipped in update even if update is True. This is useful if you have parameters that are slow to update but can be updated in a different way (as in the qdac). If you want to skip the update of certain parameters in all snapshots, use the snapshot_get attribute of those parameters instead.

Returns

base snapshot

Return type

dict

validate_status(verbose: bool = False) → None

Validate the values of all gettable parameters

The validation is done for all parameters that have both a get and set method.

Parameters

verbose – If True, then information about the parameters that are being check is printed.

parameters: Dict[str, ParameterBase] = {}

All the parameters supported by this instrument. Usually populated via add_parameter().

functions: Dict[str, Function] = {}

All the functions supported by this instrument. Usually populated via add_function().

submodules: Dict[str, Union['InstrumentModule', 'ChannelTuple']] = {}

All the submodules of this instrument such as channel lists or logical groupings of parameters. Usually populated via add_submodule().

instrument_modules: Dict[str, 'InstrumentModule'] = {}

All the InstrumentModule of this instrument Usually populated via add_submodule().

metadata: Dict[str, Any] = {}

class qcodes.instrument.VisaInstrument(*args: Any, **kwargs: Any)

Bases: Instrument

Base class for all instruments using visa connections.

Parameters

• name – What this instrument is called locally.

• address – The visa resource name to use to connect.

• timeout – seconds to allow for responses. Default 5.

• terminator – Read and write termination character(s). If None the terminator will not be set and we rely on the defaults from PyVisa. Default None.

• device_clear – Perform a device clear. Default True.

• visalib – Visa backend to use when connecting to this instrument. This should be in the form of a string ‘<pathtofile>@<backend>’. Both parts can be omitted and pyvisa will try to infer the path to the visa backend file. By default the IVI backend is used if found, but ‘@py’ will use the pyvisa-py backend. Note that QCoDeS does not install (or even require) ANY backends, it is up to the user to do that. see eg: http://pyvisa.readthedocs.org/en/stable/names.html

• metadata – additional static metadata to add to this instrument’s JSON snapshot.

See help for Instrument for additional information on writing instrument subclasses.

visa_handle

The communication channel.

Type

pyvisa.resources.Resource

set_address(address: str) → None

Set the address for this instrument.

Parameters

address – The visa resource name to use to connect. The address should be the actual address and just that. If you wish to change the backend for VISA, use the self.visalib attribute (and then call this function).

device_clear() → None

Clear the buffers of the device

set_terminator(terminator: Optional[str]) → None

Change the read terminator to use.

Parameters

terminator – Character(s) to look for at the end of a read and to end each write command with. eg. \r\n. If None the terminator will not be set.

close() → None

Disconnect and irreversibly tear down the instrument.

check_error(ret_code: int) → None

Default error checking, raises an error if return code !=0. Does not differentiate between warnings or specific error messages. Override this function in your driver if you want to add specific error messages.

Parameters

ret_code – A Visa error code. See eg: https://github.com/hgrecco/pyvisa/blob/master/pyvisa/errors.py

Raises

visa.VisaIOError – if ret_code indicates a communication problem.

write_raw(cmd: str) → None

Low-level interface to visa_handle.write.

Parameters

cmd – The command to send to the instrument.

ask_raw(cmd: str) → str

Low-level interface to visa_handle.ask.

Parameters

cmd – The command to send to the instrument.

Returns

The instrument’s response.

Return type

str

snapshot_base(update: Optional[bool] = True, params_to_skip_update: Optional[Sequence[str]] = None) → Dict[Any, Any]

State of the instrument as a JSON-compatible dict (everything that the custom JSON encoder class NumpyJSONEncoder supports).

Parameters

• update – If True, update the state by querying the instrument. If None only update if the state is known to be invalid. If False, just use the latest values in memory and never update.

• params_to_skip_update – List of parameter names that will be skipped in update even if update is True. This is useful if you have parameters that are slow to update but can be updated in a different way (as in the qdac). If you want to skip the update of certain parameters in all snapshots, use the snapshot_get attribute of those parameters instead.

Returns

base snapshot

Return type

dict

__del__() → None

Close the instrument and remove its instance record.

__getitem__(key: str) → Union[Callable[[...], Any], Parameter]

Delegate instrument[‘name’] to parameter or function ‘name’.

__getstate__() → None

Prevent pickling instruments, and give a nice error message.

__repr__() → str

Simplified repr giving just the class and name.

add_function(name: str, **kwargs: Any) → None

Bind one Function to this instrument.

Instrument subclasses can call this repeatedly in their __init__ for every real function of the instrument.

This functionality is meant for simple cases, principally things that map to simple commands like *RST (reset) or those with just a few arguments. It requires a fixed argument count, and positional args only. If your case is more complicated, you’re probably better off simply making a new method in your Instrument subclass definition.

Parameters

• name – How the Function will be stored within instrument.Functions and also how you address it using the shortcut methods: instrument.call(func_name, *args) etc.

• **kwargs – constructor kwargs for Function

Raises

KeyError – If this instrument already has a function with this name.

add_parameter(name: str, parameter_class: Optional[Type[ParameterBase]] = None, **kwargs: Any) → None

Bind one Parameter to this instrument.

Instrument subclasses can call this repeatedly in their __init__ for every real parameter of the instrument.

In this sense, parameters are the state variables of the instrument, anything the user can set and/or get.

Parameters

• name – How the parameter will be stored within parameters and also how you address it using the shortcut methods: instrument.set(param_name, value) etc.

• parameter_class – You can construct the parameter out of any class. Default parameters.Parameter.

• **kwargs – Constructor arguments for parameter_class.

Raises

• KeyError – If this instrument already has a parameter with this name and the parameter being replaced is not an abstract parameter.

• ValueError – If there is an existing abstract parameter and the unit of the new parameter is inconsistent with the existing one.

add_submodule(name: str, submodule: Union[InstrumentModule, ChannelTuple]) → None

Bind one submodule to this instrument.

Instrument subclasses can call this repeatedly in their __init__ method for every submodule of the instrument.

Submodules can effectively be considered as instruments within the main instrument, and should at minimum be snapshottable. For example, they can be used to either store logical groupings of parameters, which may or may not be repeated, or channel lists. They should either be an instance of an InstrumentModule or a ChannelTuple.

Parameters

• name – How the submodule will be stored within instrument.submodules and also how it can be addressed.

• submodule – The submodule to be stored.

Raises

• KeyError – If this instrument already contains a submodule with this name.

• TypeError – If the submodule that we are trying to add is not an instance of an Metadatable object.

property ancestors: List[qcodes.instrument.instrument_base.InstrumentBase]

Returns a list of instruments, starting from the current instrument and following to the parent instrument and the parents parent instrument until the root instrument is reached.

ask(cmd: str) → str

Write a command string to the hardware and return a response.

Subclasses that transform cmd should override this method, and in it call super().ask(new_cmd). Subclasses that define a new hardware communication should instead override ask_raw.

Parameters

cmd – The string to send to the instrument.

Returns

response

Raises

Exception – Wraps any underlying exception with extra context, including the command and the instrument.

call(func_name: str, *args: Any) → Any

Shortcut for calling a function from its name.

Parameters

• func_name – The name of a function of this instrument.

• *args – any arguments to the function.

Returns

The return value of the function.

classmethod close_all() → None

Try to close all instruments registered in _all_instruments This is handy for use with atexit to ensure that all instruments are closed when a python session is closed.

Examples

>>> atexit.register(qc.Instrument.close_all())

connect_message(idn_param: str = 'IDN', begin_time: Optional[float] = None) → None

Print a standard message on initial connection to an instrument.

Parameters

• idn_param – Name of parameter that returns ID dict. Default IDN.

• begin_time – time.time() when init started. Default is self._t0, set at start of Instrument.__init__.

delegate_attr_dicts: List[str] = ['parameters', 'functions', 'submodules']

A list of names (strings) of dictionaries which are (or will be) attributes of self, whose keys should be treated as attributes of self.

delegate_attr_objects: List[str] = []

A list of names (strings) of objects which are (or will be) attributes of self, whose attributes should be passed through to self.

static exist(name: str, instrument_class: Optional[type] = None) → bool

Check if an instrument with a given names exists (i.e. is already instantiated).

Parameters

• name – Name of the instrument.

• instrument_class – The type of instrument you are looking for.

classmethod find_instrument(name: str, instrument_class: Optional[Type[T]] = None) → T

Find an existing instrument by name.

Parameters

• name – Name of the instrument.

• instrument_class – The type of instrument you are looking for.

Returns

The instrument found.

Raises

• KeyError – If no instrument of that name was found, or if its reference is invalid (dead).

• TypeError – If a specific class was requested but a different type was found.

property full_name: str

get(param_name: str) → Any

Shortcut for getting a parameter from its name.

Parameters

param_name – The name of a parameter of this instrument.

Returns

The current value of the parameter.

get_idn() → Dict[str, Optional[str]]

Parse a standard VISA *IDN? response into an ID dict.

Even though this is the VISA standard, it applies to various other types as well, such as IPInstruments, so it is included here in the Instrument base class.

Override this if your instrument does not support *IDN? or returns a nonstandard IDN string. This string is supposed to be a comma-separated list of vendor, model, serial, and firmware, but semicolon and colon are also common separators so we accept them here as well.

Returns

A dict containing vendor, model, serial, and firmware.

classmethod instances() → List[Instrument]

Get all currently defined instances of this instrument class.

You can use this to get the objects back if you lose track of them, and it’s also used by the test system to find objects to test against.

Returns

A list of instances.

invalidate_cache() → None

Invalidate the cache of all parameters on the instrument. Calling this method will recursively mark the cache of all parameters on the instrument and any parameter on instrument modules as invalid.

This is useful if you have performed manual operations (e.g. using the frontpanel) which changes the state of the instrument outside QCoDeS.

This in turn means that the next snapshot of the instrument will trigger a (potentially slow) reread of all parameters of the instrument if you pass update=None to snapshot.

static is_valid(instr_instance: Instrument) → bool

Check if a given instance of an instrument is valid: if an instrument has been closed, its instance is not longer a “valid” instrument.

Parameters

instr_instance – Instance of an Instrument class or its subclass.

load_metadata(metadata: Mapping[str, Any]) → None

Load metadata into this classes metadata dictionary.

Parameters

metadata – Metadata to load.

property name: str

Name of the instrument This is equivalent to full_name for backwards compatibility.

property name_parts: List[str]

omit_delegate_attrs: List[str] = []

A list of attribute names (strings) to not delegate to any other dictionary or object.

property parent: Optional[qcodes.instrument.instrument_base.InstrumentBase]

Returns the parent instrument. By default this is None. Any SubInstrument should subclass this to return the parent instrument.

print_readable_snapshot(update: bool = False, max_chars: int = 80) → None

Prints a readable version of the snapshot. The readable snapshot includes the name, value and unit of each parameter. A convenience function to quickly get an overview of the status of an instrument.

Parameters

• update – If True, update the state by querying the instrument. If False, just use the latest values in memory. This argument gets passed to the snapshot function.

• max_chars – the maximum number of characters per line. The readable snapshot will be cropped if this value is exceeded. Defaults to 80 to be consistent with default terminal width.

classmethod record_instance(instance: Instrument) → None

Record (a weak ref to) an instance in a class’s instance list.

Also records the instance in list of all instruments, and verifies that there are no other instruments with the same name.

This method is called after initialization of the instrument is completed.

Parameters

instance – Instance to record.

Raises

KeyError – If another instance with the same name is already present.

classmethod remove_instance(instance: Instrument) → None

Remove a particular instance from the record.

Parameters

instance – The instance to remove

property root_instrument: qcodes.instrument.instrument_base.InstrumentBase

set(param_name: str, value: Any) → None

Shortcut for setting a parameter from its name and new value.

Parameters

• param_name – The name of a parameter of this instrument.

• value – The new value to set.

shared_kwargs = ()

property short_name: str

Short name of the instrument

snapshot(update: Optional[bool] = False) → Dict[Any, Any]

Decorate a snapshot dictionary with metadata. DO NOT override this method if you want metadata in the snapshot instead, override snapshot_base().

Parameters

update – Passed to snapshot_base.

Returns

Base snapshot.

validate_status(verbose: bool = False) → None

Validate the values of all gettable parameters

The validation is done for all parameters that have both a get and set method.

Parameters

verbose – If True, then information about the parameters that are being check is printed.

write(cmd: str) → None

Write a command string with NO response to the hardware.

Subclasses that transform cmd should override this method, and in it call super().write(new_cmd). Subclasses that define a new hardware communication should instead override write_raw.

Parameters

cmd – The string to send to the instrument.

Raises

Exception – Wraps any underlying exception with extra context, including the command and the instrument.

parameters: Dict[str, ParameterBase] = {}

All the parameters supported by this instrument. Usually populated via add_parameter().

functions: Dict[str, Function] = {}

All the functions supported by this instrument. Usually populated via add_function().

submodules: Dict[str, Union['InstrumentModule', 'ChannelTuple']] = {}

All the submodules of this instrument such as channel lists or logical groupings of parameters. Usually populated via add_submodule().

instrument_modules: Dict[str, 'InstrumentModule'] = {}

All the InstrumentModule of this instrument Usually populated via add_submodule().

metadata: Dict[str, Any] = {}

qcodes.instrument.find_or_create_instrument(instrument_class: Type[T], name: str, *args: Any, recreate: bool = False, **kwargs: Any) → T

Find an instrument with the given name of a given class, or create one if it is not found. In case the instrument was found, and recreate is True, the instrument will be re-instantiated.

Note that the class of the existing instrument has to be equal to the instrument class of interest. For example, if an instrument with the same name but of a different class exists, the function will raise an exception.

This function is very convenient because it allows not to bother about which instruments are already instantiated and which are not.

If an instrument is found, a connection message is printed, as if the instrument has just been instantiated.

Parameters

• instrument_class – Class of the instrument to find or create.

• name – Name of the instrument to find or create.

• recreate – When True, the instruments gets recreated if it is found.

Returns

The found or created instrument.