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# Copyright (c) 2010-2012 testtools developers. See LICENSE for details.
from collections.abc import Callable
from typing import Any, TypeVar
T = TypeVar("T")
K = TypeVar("K")
V = TypeVar("V")
R = TypeVar("R")
def map_values(function: Callable[[V], R], dictionary: dict[K, V]) -> dict[K, R]:
"""Map ``function`` across the values of ``dictionary``.
:return: A dict with the same keys as ``dictionary``, where the value
of each key ``k`` is ``function(dictionary[k])``.
"""
return {k: function(dictionary[k]) for k in dictionary}
def filter_values(function: Callable[[V], bool], dictionary: dict[K, V]) -> dict[K, V]:
"""Filter ``dictionary`` by its values using ``function``."""
return {k: v for k, v in dictionary.items() if function(v)}
def dict_subtract(a: dict[K, V], b: dict[K, Any]) -> dict[K, V]:
"""Return the part of ``a`` that's not in ``b``."""
return {k: a[k] for k in set(a) - set(b)}
def list_subtract(a: list[T], b: list[T]) -> list[T]:
"""Return a list ``a`` without the elements of ``b``.
If a particular value is in ``a`` twice and ``b`` once then the returned
list then that value will appear once in the returned list.
"""
a_only = list(a)
for x in b:
if x in a_only:
a_only.remove(x)
return a_only
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