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# SPDX-License-Identifier: MIT | ||
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from __future__ import absolute_import, division, print_function | ||
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import functools | ||
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from ._compat import new_class | ||
from ._make import _make_ne | ||
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_operation_names = {"eq": "==", "lt": "<", "le": "<=", "gt": ">", "ge": ">="} | ||
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def cmp_using( | ||
eq=None, | ||
lt=None, | ||
le=None, | ||
gt=None, | ||
ge=None, | ||
require_same_type=True, | ||
class_name="Comparable", | ||
): | ||
""" | ||
Create a class that can be passed into `attr.ib`'s ``eq``, ``order``, and | ||
``cmp`` arguments to customize field comparison. | ||
The resulting class will have a full set of ordering methods if | ||
at least one of ``{lt, le, gt, ge}`` and ``eq`` are provided. | ||
:param Optional[callable] eq: `callable` used to evaluate equality | ||
of two objects. | ||
:param Optional[callable] lt: `callable` used to evaluate whether | ||
one object is less than another object. | ||
:param Optional[callable] le: `callable` used to evaluate whether | ||
one object is less than or equal to another object. | ||
:param Optional[callable] gt: `callable` used to evaluate whether | ||
one object is greater than another object. | ||
:param Optional[callable] ge: `callable` used to evaluate whether | ||
one object is greater than or equal to another object. | ||
:param bool require_same_type: When `True`, equality and ordering methods | ||
will return `NotImplemented` if objects are not of the same type. | ||
:param Optional[str] class_name: Name of class. Defaults to 'Comparable'. | ||
See `comparison` for more details. | ||
.. versionadded:: 21.1.0 | ||
""" | ||
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body = { | ||
"__slots__": ["value"], | ||
"__init__": _make_init(), | ||
"_requirements": [], | ||
"_is_comparable_to": _is_comparable_to, | ||
} | ||
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# Add operations. | ||
num_order_functions = 0 | ||
has_eq_function = False | ||
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if eq is not None: | ||
has_eq_function = True | ||
body["__eq__"] = _make_operator("eq", eq) | ||
body["__ne__"] = _make_ne() | ||
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if lt is not None: | ||
num_order_functions += 1 | ||
body["__lt__"] = _make_operator("lt", lt) | ||
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if le is not None: | ||
num_order_functions += 1 | ||
body["__le__"] = _make_operator("le", le) | ||
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if gt is not None: | ||
num_order_functions += 1 | ||
body["__gt__"] = _make_operator("gt", gt) | ||
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if ge is not None: | ||
num_order_functions += 1 | ||
body["__ge__"] = _make_operator("ge", ge) | ||
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type_ = new_class(class_name, (object,), {}, lambda ns: ns.update(body)) | ||
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# Add same type requirement. | ||
if require_same_type: | ||
type_._requirements.append(_check_same_type) | ||
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# Add total ordering if at least one operation was defined. | ||
if 0 < num_order_functions < 4: | ||
if not has_eq_function: | ||
# functools.total_ordering requires __eq__ to be defined, | ||
# so raise early error here to keep a nice stack. | ||
raise ValueError( | ||
"eq must be define is order to complete ordering from " | ||
"lt, le, gt, ge." | ||
) | ||
type_ = functools.total_ordering(type_) | ||
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return type_ | ||
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def _make_init(): | ||
""" | ||
Create __init__ method. | ||
""" | ||
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def __init__(self, value): | ||
""" | ||
Initialize object with *value*. | ||
""" | ||
self.value = value | ||
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return __init__ | ||
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def _make_operator(name, func): | ||
""" | ||
Create operator method. | ||
""" | ||
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def method(self, other): | ||
if not self._is_comparable_to(other): | ||
return NotImplemented | ||
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result = func(self.value, other.value) | ||
if result is NotImplemented: | ||
return NotImplemented | ||
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return result | ||
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method.__name__ = "__%s__" % (name,) | ||
method.__doc__ = "Return a %s b. Computed by attrs." % ( | ||
_operation_names[name], | ||
) | ||
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return method | ||
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def _is_comparable_to(self, other): | ||
""" | ||
Check whether `other` is comparable to `self`. | ||
""" | ||
for func in self._requirements: | ||
if not func(self, other): | ||
return False | ||
return True | ||
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def _check_same_type(self, other): | ||
""" | ||
Return True if *self* and *other* are of the same type, False otherwise. | ||
""" | ||
return other.value.__class__ is self.value.__class__ |
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