1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
|
from __future__ import absolute_import, division, print_function
import functools
from ._compat import new_class
from ._make import _make_ne
_operation_names = {"eq": "==", "lt": "<", "le": "<=", "gt": ">", "ge": ">="}
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
"""
body = {
"__slots__": ["value"],
"__init__": _make_init(),
"_requirements": [],
"_is_comparable_to": _is_comparable_to,
}
# Add operations.
num_order_functions = 0
has_eq_function = False
if eq is not None:
has_eq_function = True
body["__eq__"] = _make_operator("eq", eq)
body["__ne__"] = _make_ne()
if lt is not None:
num_order_functions += 1
body["__lt__"] = _make_operator("lt", lt)
if le is not None:
num_order_functions += 1
body["__le__"] = _make_operator("le", le)
if gt is not None:
num_order_functions += 1
body["__gt__"] = _make_operator("gt", gt)
if ge is not None:
num_order_functions += 1
body["__ge__"] = _make_operator("ge", ge)
type_ = new_class(class_name, (object,), {}, lambda ns: ns.update(body))
# Add same type requirement.
if require_same_type:
type_._requirements.append(_check_same_type)
# 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_)
return type_
def _make_init():
"""
Create __init__ method.
"""
def __init__(self, value):
"""
Initialize object with *value*.
"""
self.value = value
return __init__
def _make_operator(name, func):
"""
Create operator method.
"""
def method(self, other):
if not self._is_comparable_to(other):
return NotImplemented
result = func(self.value, other.value)
if result is NotImplemented:
return NotImplemented
return result
method.__name__ = "__%s__" % (name,)
method.__doc__ = "Return a %s b. Computed by attrs." % (
_operation_names[name],
)
return method
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
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__
|
