Utilities

qiskit.utils.add_deprecation_to_docstring(func, msg, *, since, pending)

Dynamically insert the deprecation message into func’s docstring.

Parameters

• func (Callable) – The function to modify.
• msg (str) – The full deprecation message.
• since (str | None) – The version the deprecation started at.
• pending (bool) – Is the deprecation still pending?

qiskit.utils.deprecate_arg(name, *, since, additional_msg=None, deprecation_description=None, pending=False, package_name='qiskit', new_alias=None, predicate=None, removal_timeline='no earlier than 3 months after the release date')

Decorator to indicate an argument has been deprecated in some way.

This decorator may be used multiple times on the same function, once per deprecated argument. It should be placed beneath other decorators like @staticmethod and property decorators.

Parameters

• name (str) – The name of the deprecated argument.
• since (str) – The version the deprecation started at. If the deprecation is pending, set the version to when that started; but later, when switching from pending to deprecated, update since to the new version.
• deprecation_description (str | None) – What is being deprecated? E.g. “Setting my_func()’s my_arg argument to None.” If not set, will default to “{func_name}’s argument {name}”.
• additional_msg (str | None) – Put here any additional information, such as what to use instead (if new_alias is not set). For example, “Instead, use the argument new_arg, which is similar but does not impact the circuit’s setup.”
• pending (bool) – Set to True if the deprecation is still pending.
• package_name (str) – The PyPI package name, e.g. “qiskit-nature”.
• new_alias (str | None) – If the arg has simply been renamed, set this to the new name. The decorator will dynamically update the kwargs so that when the user sets the old arg, it will be passed in as the new_alias arg.
• predicate (Callable[[Any], bool] | None) – Only log the runtime warning if the predicate returns True. This is useful to deprecate certain values or types for an argument, e.g. lambda my_arg: isinstance(my_arg, dict). Regardless of if a predicate is set, the runtime warning will only log when the user specifies the argument.
• removal_timeline (str) – How soon can this deprecation be removed? Expects a value like “no sooner than 6 months after the latest release” or “in release 9.99”.

Returns

The decorated callable.

Return type

Callable

qiskit.utils.deprecate_arguments(kwarg_map, category=<class 'DeprecationWarning'>, *, since=None)

Deprecated. Instead, use @deprecate_arg.

Parameters

• kwarg_map (dict[str, str | None]) – A dictionary of the old argument name to the new name.
• category (Type[Warning]) – Usually either DeprecationWarning or PendingDeprecationWarning.
• since (str | None) – The version the deprecation started at. Only Optional for backwards compatibility - this should always be set. If the deprecation is pending, set the version to when that started; but later, when switching from pending to deprecated, update since to the new version.

Returns

The decorated callable.

Return type

Callable

qiskit.utils.deprecate_func(*, since, additional_msg=None, pending=False, package_name='qiskit', removal_timeline='no earlier than 3 months after the release date', is_property=False)

Decorator to indicate a function has been deprecated.

It should be placed beneath other decorators like @staticmethod and property decorators.

When deprecating a class, set this decorator on its __init__ function.

Parameters

• since (str) – The version the deprecation started at. If the deprecation is pending, set the version to when that started; but later, when switching from pending to deprecated, update since to the new version.
• additional_msg (str | None) – Put here any additional information, such as what to use instead. For example, “Instead, use the function new_func from the module <my_module>.<my_submodule>, which is similar but uses GPU acceleration.”
• pending (bool) – Set to True if the deprecation is still pending.
• package_name (str) – The PyPI package name, e.g. “qiskit-nature”.
• removal_timeline (str) – How soon can this deprecation be removed? Expects a value like “no sooner than 6 months after the latest release” or “in release 9.99”.
• is_property (bool) – If the deprecated function is a @property, set this to True so that the generated message correctly describes it as such. (This isn’t necessary for property setters, as their docstring is ignored by Python.)

Returns

The decorated callable.

Return type

Callable

qiskit.utils.deprecate_function(msg, stacklevel=2, category=<class 'DeprecationWarning'>, *, since=None)

Deprecated. Instead, use @deprecate_func.

Parameters

• msg (str) – Warning message to emit.
• stacklevel (int) – The warning stacklevel to use, defaults to 2.
• category (Type[Warning]) – Usually either DeprecationWarning or PendingDeprecationWarning.
• since (str | None) – The version the deprecation started at. Only Optional for backwards compatibility - this should always be set. If the deprecation is pending, set the version to when that started; but later, when switching from pending to deprecated, update since to the new version.

Returns

The decorated, deprecated callable.

Return type

Callable

qiskit.utils.apply_prefix(value, unit)

Given a SI unit prefix and value, apply the prefix to convert to standard SI unit.

Parameters

• value (float |ParameterExpression) – The number to apply prefix to.
• unit (str) – String prefix.

Returns

Converted value.

Return type

float | ParameterExpression

Raises

ValueError – If the units aren’t recognized.

Return type

float | ParameterExpression

qiskit.utils.detach_prefix(value, decimal=None)

Given a SI unit value, find the most suitable prefix to scale the value.

For example, the value = 1.3e8 will be converted into a tuple of (130.0, "M"), which represents a scaled value and auxiliary unit that may be used to display the value. In above example, that value might be displayed as 130 MHz (unit is arbitrary here).

Example

>>> value, prefix = detach_prefix(1e4)
>>> print(f"{value} {prefix}Hz")
10 kHz

Parameters

• value (float) – The number to find prefix.
• decimal (int | None) – Optional. An arbitrary integer number to represent a precision of the value. If specified, it tries to round the mantissa and adjust the prefix to rounded value. For example, 999_999.91 will become 999.9999 k with decimal=4, while 1.0 M with decimal=3 or less.

Returns

A tuple of scaled value and prefix.

Return type

tuple[float, str]

Raises

• ValueError – If the value is out of range.
• ValueError – If the value is not real number.

Return type

tuple[float, str]

qiskit.utils.wrap_method(cls, name, *, before=None, after=None)

Wrap the functionality the instance- or class method cls.name with additional behaviour before and after.

This mutates cls, replacing the attribute name with the new functionality. This is useful when creating class decorators. The method is allowed to be defined on any parent class instead.

If either before or after are given, they should be callables with a compatible signature to the method referred to. They will be called immediately before or after the method as appropriate, and any return value will be ignored.

Parameters

• cls (Type) – the class to modify.
• name (str) – the name of the method on the class to wrap.
• before (Callable | None) – a callable that should be called before the method that is being wrapped.
• after (Callable | None) – a callable that should be called after the method that is being wrapped.

Raises

ValueError – if the named method is not defined on the class or any parent class.

qiskit.utils.local_hardware_info()

Basic hardware information about the local machine.

Gives actual number of CPU’s in the machine, even when hyperthreading is turned on. CPU count defaults to 1 when true count can’t be determined.

Returns

The hardware information.

Return type

dict

qiskit.utils.is_main_process()

Checks whether the current process is the main one

qiskit.utils.parallel_map(task, values, task_args=(), task_kwargs={}, num_processes=2)

Parallel execution of a mapping of values to the function task. This is functionally equivalent to:

result = [task(value, *task_args, **task_kwargs) for value in values]

This will parallelise the results if the number of values is greater than one, and the current system configuration permits parallelization.

Parameters

• task (func) – Function that is to be called for each value in values.
• values (array_like) – List or array of values for which the task function is to be evaluated.
• task_args (list) – Optional additional arguments to the task function.
• task_kwargs (dict) – Optional additional keyword argument to the task function.
• num_processes (int) – Number of processes to spawn.

Returns

The result list contains the value of task(value, *task_args, **task_kwargs) for each value in values.

Return type

result

Raises

QiskitError – If user interrupts via keyboard.

Examples

import time
from qiskit.utils import parallel_map
def func(_):
        time.sleep(0.1)
        return 0
parallel_map(func, list(range(10)));