qcodes.instrument.specialized_parameters

Module for specialized parameters. The qcodes.instrument.parameter module provides generic parameters for different generic cases. This module provides useful/convenient specializations of such generic parameters.

class qcodes.instrument.specialized_parameters.ElapsedTimeParameter(name: str, label: str = 'Elapsed time', **kwargs: Any)[source]

Bases: qcodes.instrument.parameter.Parameter

Parameter to measure elapsed time. Measures wall clock time since the last reset of the instance’s clock. The clock is reset upon creation of the instance. The constructor passes kwargs along to the Parameter constructor.

Parameters

name – The local name of the parameter. See the documentation of qcodes.instrument.parameter.Parameter for more details.

get_raw() float[source]

get_raw is called to perform the actual data acquisition from the instrument. This method should either be overwritten to perform the desired operation or alternatively for Parameter a suitable method is automatically generated if get_cmd is supplied to the parameter constructor. The method is automatically wrapped to provide a get method on the parameter instance.

reset_clock() None[source]
property t0: float
__getitem__(keys: Any) qcodes.instrument.sweep_values.SweepFixedValues

Slice a Parameter to get a SweepValues object to iterate over during a sweep

__str__() str

Include the instrument name with the Parameter name if possible.

property abstract: Optional[bool]
property full_name: str

Name of the parameter including the name of the instrument and submodule that the parameter may be bound to. The names are separated by underscores, like this: instrument_submodule_parameter.

get_ramp_values(value: Union[float, Sized], step: Optional[float] = None) Sequence[Union[float, Sized]]

Return values to sweep from current value to target value. This method can be overridden to have a custom sweep behaviour. It can even be overridden by a generator.

Parameters
  • value – target value

  • step – maximum step size

Returns

List of stepped values, including target value.

property gettable: bool

Is it allowed to call get on this parameter?

increment(value: Any) None

Increment the parameter with a value

Parameters

value – Value to be added to the parameter.

property instrument: Optional[InstrumentBase]

Return the first instrument that this parameter is bound to. E.g if this is bound to a channel it will return the channel and not the instrument that the channel is bound too. Use root_instrument() to get the real instrument.

property inter_delay: float

Delay time between consecutive set operations. The actual time will not be shorter than this, but may be longer if the underlying set call takes longer.

Typically used in conjunction with step to create an effective ramp rate, but can also be used without a step to enforce a delay between sets.

Getter

Returns the current inter_delay.

Setter

Sets the value of the inter_delay.

Raises
load_metadata(metadata: Dict[Any, Any]) None

Load metadata into this classes metadata dictionary.

Parameters

metadata – Metadata to load.

property name: str

Name of the parameter. This is identical to short_name().

property name_parts: List[str]

List of the parts that make up the full name of this parameter

property post_delay: float

Delay time after start of set operation, for each set. The actual time will not be shorter than this, but may be longer if the underlying set call takes longer.

Typically used in conjunction with step to create an effective ramp rate, but can also be used without a step to enforce a delay after every set. One might think of post_delay as how long a set operation is supposed to take. For example, there might be an instrument that needs extra time after setting a parameter although the command for setting the parameter returns quickly.

Getter

Returns the current post_delay.

Setter

Sets the value of the post_delay.

Raises
property raw_value: Any

Note that this property will be deprecated soon. Use cache.raw_value instead.

Represents the cached raw value of the parameter.

Getter

Returns the cached raw value of the parameter.

restore_at_exit(allow_changes: bool = True) qcodes.instrument.parameter._SetParamContext

Use a context manager to restore the value of a parameter after a with block.

By default, the parameter value may be changed inside the block, but this can be prevented with allow_changes=False. This can be useful, for example, for debugging a complex measurement that unintentionally modifies a parameter.

Example

>>> p = Parameter("p", set_cmd=None, get_cmd=None)
>>> p.set(2)
>>> with p.restore_at_exit():
...     p.set(3)
...     print(f"value inside with block: {p.get()}")  # prints 3
>>> print(f"value after with block: {p.get()}")  # prints 2
>>> with p.restore_at_exit(allow_changes=False):
...     p.set(5)  # raises an exception
property root_instrument: Optional[InstrumentBase]

Return the fundamental instrument that this parameter belongs too. E.g if the parameter is bound to a channel this will return the fundamental instrument that that channel belongs to. Use instrument() to get the channel.

set_raw(value: Any) None

set_raw is called to perform the actual setting of a parameter on the instrument. This method should either be overwritten to perform the desired operation or alternatively for Parameter a suitable method is automatically generated if set_cmd is supplied to the parameter constructor. The method is automatically wrapped to provide a set method on the parameter instance.

set_to(value: Any, allow_changes: bool = False) qcodes.instrument.parameter._SetParamContext

Use a context manager to temporarily set a parameter to a value. By default, the parameter value cannot be changed inside the context. This may be overridden with allow_changes=True.

Examples

>>> from qcodes import Parameter
>>> p = Parameter("p", set_cmd=None, get_cmd=None)
>>> p.set(2)
>>> with p.set_to(3):
...     print(f"p value in with block {p.get()}")  # prints 3
...     p.set(5)  # raises an exception
>>> print(f"p value outside with block {p.get()}")  # prints 2
>>> with p.set_to(3, allow_changes=True):
...     p.set(5)  # now this works
>>> print(f"value after second block: {p.get()}")  # still prints 2
property settable: bool

Is it allowed to call set on this parameter?

property short_name: str

Short name of the parameter. This is without the name of the instrument or submodule that the parameter may be bound to. For full name refer to full_name().

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 parameter as a JSON-compatible dict (everything that the custom JSON encoder class qcodes.utils.helpers.NumpyJSONEncoder supports).

If the parameter has been initiated with snapshot_value=False, the snapshot will NOT include the value and raw_value of the parameter.

Parameters
  • update – If True, update the state by calling parameter.get() unless snapshot_get of the parameter is False. If update is None, use the current value from the cache unless the cache is invalid. If False, never call parameter.get().

  • params_to_skip_update – No effect but may be passed from superclass

Returns

base snapshot

property snapshot_value: bool

If True the value of the parameter will be included in the snapshot.

property step: Optional[float]

Stepsize that this Parameter uses during set operation. Stepsize must be a positive number or None. If step is a positive number, this is the maximum value change allowed in one hardware call, so a single set can result in many calls to the hardware if the starting value is far from the target. All but the final change will attempt to change by +/- step exactly. If step is None stepping will not be used.

Getter

Returns the current stepsize.

Setter

Sets the value of the step.

Raises
  • TypeError – if step is set to not numeric or None

  • ValueError – if step is set to negative

  • TypeError – if step is set to not integer or None for an integer parameter

  • TypeError – if step is set to not a number on None

sweep(start: float, stop: float, step: Optional[float] = None, num: Optional[int] = None) qcodes.instrument.sweep_values.SweepFixedValues

Create a collection of parameter values to be iterated over. Requires start and stop and (step or num) The sign of step is not relevant.

Parameters
  • start – The starting value of the sequence.

  • stop – The end value of the sequence.

  • step – Spacing between values.

  • num – Number of values to generate.

Returns

Collection of parameter values to be iterated over.

Return type

SweepFixedValues

Examples

>>> sweep(0, 10, num=5)
 [0.0, 2.5, 5.0, 7.5, 10.0]
>>> sweep(5, 10, step=1)
[5.0, 6.0, 7.0, 8.0, 9.0, 10.0]
>>> sweep(15, 10.5, step=1.5)
>[15.0, 13.5, 12.0, 10.5]
property underlying_instrument: Optional[InstrumentBase]

Returns an instance of the underlying hardware instrument that this parameter communicates with, per this parameter’s implementation.

This is useful in the case where a parameter does not belongs to an instrument instance that represents a real hardware instrument but actually uses a real hardware instrument in its implementation (e.g. via calls to one or more parameters of that real hardware instrument). This is also useful when a parameter does belong to an instrument instance but that instance does not represent the real hardware instrument that the parameter interacts with: hence root_instrument of the parameter cannot be the hardware_instrument, however underlying_instrument can be implemented to return the hardware_instrument.

By default it returns the root_instrument of the parameter.

validate(value: Any) None

Validate the value supplied.

Parameters

value – value to validate

Raises
  • TypeError – If the value is of the wrong type.

  • ValueError – If the value is outside the bounds specified by the validator.

label: str = ()

Label of the data used for plots etc.

cache: _CacheProtocol = ()
get_latest: GetLatest = ()
get: Callable[..., ParamDataType] = ()
set: Callable[..., None] = ()
unit = ()

The unit of measure. Use '' for unitless.