#!/usr/bin/env python
#
# getters.py
"""
Variants of :func:`operator.attrgetter`, :func:`operator.itemgetter` and :func:`operator.methodcaller`
which operate on values within sequences.
.. versionadded:: 3.2.0
""" # noqa: D400
#
# Copyright © 2021 Dominic Davis-Foster <dominic@davis-foster.co.uk>
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
# IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
# DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
# OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE
# OR OTHER DEALINGS IN THE SOFTWARE.
#
# Adapted from https://github.com/python/cpython/blob/master/Lib/operator.py
# Licensed under the Python Software Foundation License Version 2.
# Copyright © 2001-2020 Python Software Foundation. All rights reserved.
# Copyright © 2000 BeOpen.com. All rights reserved.
# Copyright © 1995-2000 Corporation for National Research Initiatives. All rights reserved.
# Copyright © 1991-1995 Stichting Mathematisch Centrum. All rights reserved.
#
# stdlib
from functools import partial
from typing import TYPE_CHECKING, Any, Dict, Tuple
__all__ = ["attrgetter", "itemgetter", "methodcaller"]
[docs]class attrgetter:
"""
Returns a callable object that fetches ``attr`` from the item at index ``idx`` in its operand.
The attribute name can contain dots. For example:
* After ``f = attrgetter(0, 'name')``, the call call ``f(b)`` returns ``b[0].name``.
* After ``f = attrgetter(3, 'name.first')``, the call ``f(b)`` returns ``b[3].name.first``.
.. code-block:: python
>>> from pathlib import Path
>>> attrgetter(0, 'name')([Path("dir/code.py")])
'code.py'
>>> attrgetter(2, 'parent.name')([Path("dir/coincidence.py"), Path("dir/wheel.py"), Path("dir/operator.py")])
'dir'
.. seealso:: :func:`operator.attrgetter` and :func:`operator.itemgetter`
:param idx: The index of the item to obtain the attribute from.
:param attr: The name of the attribute.
"""
__slots__ = ("_attrs", "_call")
def __init__(self, idx: int, attr: str):
if not isinstance(idx, int):
raise TypeError("'idx' must be an integer")
if not isinstance(attr, str):
raise TypeError("attribute name must be a string")
self._attrs: Dict[str, Any] = {"idx": idx, "attr": attr}
def __call__(self, obj: Any) -> Any: # noqa: D102
names = self._attrs["attr"].split('.')
obj = obj[self._attrs["idx"]]
for name in names:
obj = getattr(obj, name)
return obj
def __repr__(self) -> str:
data = {**self._attrs, "module": self.__class__.__module__, "qualname": self.__class__.__qualname__}
return "{module}.{qualname}(idx={idx}, attr={attr!r})".format_map(data)
def __reduce__(self):
return self.__class__, tuple(self._attrs.values())
[docs]class itemgetter:
"""
Returns a callable object that fetches ``item`` from the item at index ``idx`` in its operand,
using the ``__getitem__()`` method.
For example:
* After ``f = itemgetter(0, 2)``, the call call ``f(r)`` returns ``r[0][2]``.
* After ``g = itemgetter(3, 5)``, the call ``g(r)`` returns ``r[3][5]``.
The items can be any type accepted by the item's ``__getitem__()`` method.
Dictionaries accept any hashable value. Lists, tuples, and strings accept an index or a slice:
.. code-block:: python
>>> itemgetter(0, 1)(['ABCDEFG'])
'B'
>>> itemgetter(1, 2)(['ABC', 'DEF'])
'F'
>>> itemgetter(0, slice(2, None))(['ABCDEFG'])
'CDEFG'
>>> army = [dict(rank='captain', name='Blackadder'), dict(rank='Private', name='Baldrick')]
>>> itemgetter(0, 'rank')(army)
'captain'
.. seealso:: :func:`operator.itemgetter`
:param idx: The index of the item to call ``__getitem__()`` on.
:param item: The value to pass to ``__getitem__()``.
""" # noqa: D400
__slots__ = ("_items", "_call")
def __init__(self, idx: int, item: Any):
if not isinstance(idx, int):
raise TypeError("'idx' must be an integer")
self._items: Dict[str, Any] = {"idx": idx, "item": item}
def __call__(self, obj: Any) -> Any: # noqa: D102
return obj[self._items["idx"]][self._items["item"]]
def __repr__(self) -> str:
data = {**self._items, "module": self.__class__.__module__, "qualname": self.__class__.__qualname__}
return "{module}.{qualname}(idx={idx}, item={item!r})".format_map(data)
def __reduce__(self):
return self.__class__, tuple(self._items.values())
[docs]class methodcaller:
r"""
Returns a callable object that calls the method name on the item at index ``idx`` in its operand.
If additional arguments and/or keyword arguments are given, they will be passed to the method as well.
For example:
* After ``f = methodcaller(0, 'name')``, the call ``f(b)`` returns ``b[0].name()``.
* After ``f = methodcaller(1, 'name', 'foo', bar=1)``, the call ``f(b)`` returns ``b[1].name('foo', bar=1)``.
.. code-block:: python
>>> from datetime import date
>>> methodcaller(0, 'upper')(["hello", "world"])
'HELLO'
>>> methodcaller(1, 'center', 9, "=")(["hello", "world"])
'==world=='
>>> methodcaller(0, 'replace', year=2019)([date(2021, 7, 6)])
datetime.date(2019, 7, 6)
.. seealso:: :func:`operator.methodcaller` and :func:`operator.itemgetter`
:param \_idx: The index of the item to call the method on.
:param \_attr: The name of the method to call.
:param \*args: Positional arguments to pass to the method.
:param \*\*kwargs: Keyword arguments to pass to the method.
"""
__slots__ = ("_idx", "_name", "_args", "_kwargs")
_idx: int
_name: str
_args: Tuple[Any, ...]
_kwargs: Dict[str, Any]
if TYPE_CHECKING:
def __init__(__self, __idx: int, __name: str, *args, **kwargs):
if not isinstance(__idx, int):
raise TypeError("'idx' must be an integer")
if not isinstance(__name, str):
raise TypeError("method name must be a string")
__self._idx = __idx
__self._name = __name
__self._args = args
__self._kwargs = kwargs
else:
def __init__(_self, _idx: int, _name: str, *args, **kwargs):
if not isinstance(_idx, int):
raise TypeError("'_idx' must be an integer")
if not isinstance(_name, str):
raise TypeError("method name must be a string")
_self._idx = _idx
_self._name = _name
_self._args = args
_self._kwargs = kwargs
def __call__(self, obj: Any) -> Any: # noqa: D102
return getattr(obj[self._idx], self._name)(*self._args, **self._kwargs)
def __repr__(self) -> str:
args = [repr(self._idx), repr(self._name)]
args.extend(map(repr, self._args))
args.extend(f'{k}={v!r}' for k, v in self._kwargs.items())
return f'{self.__class__.__module__}.{self.__class__.__name__}({", ".join(args)})'
def __reduce__(self):
if not self._kwargs:
return self.__class__, (self._idx, self._name) + self._args
else:
return partial(self.__class__, self._idx, self._name, **self._kwargs), self._args