CheckUnits

class plasmapy.utils.decorators.checks.CheckUnits(checks_on_return: Unit | list[Unit] | dict[str, Any] = None, **checks: Unit | list[Unit] | dict[str, Any])

Bases: CheckBase

A decorator class to ‘check’ — limit/control — the units of input and return arguments to a function or method.

Parameters:

• checks_on_return (list of units or dict of unit specifications) – Specifications for unit checks on the return of the function being wrapped. (see check units for valid specifications)

• **checks (list of astropy units or dict of unit specifications) –

  Specifications for unit checks on the input arguments of the function being wrapped. Each keyword argument in checks is the name of a function argument to be checked and the keyword value contains the unit check specifications.

  Unit checks can be defined by passing one of the astropy units, a list of astropy units, or a dictionary containing the keys defined below. Units can also be defined with function annotations, but must be consistent with decorator **checks arguments if used concurrently. If a key is omitted, then the default value will be assumed.

  Key	Type	Description
  units		list of desired astropy units
  equivalencies		[DEFAULT None] A list of equivalent pairs to try if the units are not directly convertible. (see equivalencies, and/or astropy equivalencies)
  pass_equivalent_units	bool	[DEFAULT False] allow equivalent units to pass

Notes

• Checking of function arguments *args and **kwargs is not supported.

• Decorator does NOT perform any unit conversions.

• If it is desired that None values do not raise errors or warnings, then include None in the list of units or as a default value for the function argument.

• If units are not specified in checks, then the decorator will attempt to identify desired units by examining the function annotations.

Examples

Define units with decorator parameters:

import astropy.units as u
from plasmapy.utils.decorators import CheckUnits

@CheckUnits(arg1={"units": u.cm}, arg2=u.cm, checks_on_return=[u.cm, u.km])
def foo(arg1, arg2):
    return arg1 + arg2


# or on a method
class Foo:
    @CheckUnits(arg1={"units": u.cm}, arg2=u.cm, checks_on_return=[u.cm, u.km])
    def bar(self, arg1, arg2):
        return arg1 + arg2

Define units with function annotations:

@CheckUnits()
def foo(arg1: u.cm, arg2: u.cm) -> u.cm:
    return arg1 + arg2


# or on a method
class Foo:
    @CheckUnits()
    def bar(self, arg1: u.cm, arg2: u.cm) -> u.cm:
        return arg1 + arg2

Allow None values to pass, on input and output:

@CheckUnits(checks_on_return=[u.cm, None])
def foo(arg1: u.cm = None):
    return arg1

Allow return values to have equivalent units:

@CheckUnits(
    arg1={"units": u.cm},
    checks_on_return={"units": u.km, "pass_equivalent_units": True},
)
def foo(arg1):
    return arg1

Allow equivalent units to pass with specified equivalencies:

@CheckUnits(
    arg1={
        "units": u.K,
        "equivalencies": u.temperature_energy(),
        "pass_equivalent_units": True,
    }
)
def foo(arg1):
    return arg1

Attributes Summary

checks

Requested checks on the decorated function's input arguments and/or return.

Methods Summary

__call__(f)

Decorate a function.

Attributes Documentation

checks

Requested checks on the decorated function’s input arguments and/or return.

Methods Documentation

__call__(f)

Decorate a function.

Parameters:

f – Function to be wrapped

Returns:

wrapped function of f

Return type:

function