Coverage for versio/comparable_mixin.py : 82%
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1# coding=utf-8
2"""
3 http://regebro.wordpress.com/2010/12/13/python-implementing-rich-comparison-the-correct-way/
4"""
6__docformat__ = 'restructuredtext en'
9def _cmp(a, b):
10 if a < b:
11 return -1
12 elif a > b:
13 return 1
14 else:
15 return 0
18class ComparableMixin(object):
19 """
20 Mix in this class and implement a **_cmpkey()** method to make an object comparable.
21 """
22 def _compare(self, other, method):
23 """
24 Compare an object with this object using the given comparison method.
26 :param other: object ot compare with
27 :type other: ComparableMixin
28 :param method: a comparison method
29 :type method: lambda
30 :return: asserted if comparison is true
31 :rtype: bool
32 :raises: NotImplemented
33 """
34 try:
35 return method(self._cmpkey(), other._cmpkey())
36 except (AttributeError, TypeError):
37 # _cmpkey not implemented, or return different type,
38 # so I can't compare with "other".
39 return NotImplemented
41 def _cmpkey(self):
42 """
43 The comparison key must be implemented by the child class and used by the comparison operators.
44 """
45 raise NotImplementedError
47 def __lt__(self, other):
48 """
49 less than
51 :param other: the instance to compare to
52 :type other: ComparableMixin
53 """
54 return self._compare(other, lambda s, o: _cmp(s, o) < 0)
56 def __le__(self, other):
57 """
58 less than or equal
60 :param other: the instance to compare to
61 :type other: ComparableMixin
62 """
63 return self._compare(other, lambda s, o: _cmp(s, o) <= 0)
65 def __eq__(self, other):
66 """
67 equal
69 :param other: the instance to compare to
70 :type other: ComparableMixin
71 """
72 return self._compare(other, lambda s, o: _cmp(s, o) == 0)
74 def __ge__(self, other):
75 """
76 greater than or equal
78 :param other: the instance to compare to
79 :type other: ComparableMixin
80 """
81 return self._compare(other, lambda s, o: _cmp(s, o) >= 0)
83 def __gt__(self, other):
84 """
85 greater than
87 :param other: the instance to compare to
88 :type other: ComparableMixin
89 """
90 return self._compare(other, lambda s, o: _cmp(s, o) > 0)
92 def __ne__(self, other):
93 """
94 not equal
96 :param other: the instance to compare to
97 :type other: ComparableMixin
98 """
99 return self._compare(other, lambda s, o: _cmp(s, o) != 0)