cpython/Lib/test/test_compare.py

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import unittest
class Empty:
def __repr__(self):
return '<Empty>'
class Cmp:
def __init__(self,arg):
self.arg = arg
def __repr__(self):
return '<Cmp %s>' % self.arg
Restructure comparison dramatically. There is no longer a default *ordering* between objects; there is only a default equality test (defined by an object being equal to itself only). Read the comment in object.c. The current implementation never uses a three-way comparison to compute a rich comparison, but it does use a rich comparison to compute a three-way comparison. I'm not quite done ripping out all the calls to PyObject_Compare/Cmp, or replacing tp_compare implementations with tp_richcompare implementations; but much of that has happened (to make most unit tests pass). The following tests still fail, because I need help deciding or understanding: test_codeop -- depends on comparing code objects test_datetime -- need Tim Peters' opinion test_marshal -- depends on comparing code objects test_mutants -- need help understanding it The problem with test_codeop and test_marshal is this: these tests compare two different code objects and expect them to be equal. Is that still a feature we'd like to support? I've temporarily removed the comparison and hash code from code objects, so they use the default (equality by pointer only) comparison. For the other two tests, run them to see for yourself. (There may be more failing test with "-u all".) A general problem with getting lots of these tests to pass is the reality that for object types that have a natural total ordering, implementing __cmp__ is much more convenient than implementing __eq__, __ne__, __lt__, and so on. Should we go back to allowing __cmp__ to provide a total ordering? Should we provide some other way to implement rich comparison with a single method override? Alex proposed a __key__() method; I've considered a __richcmp__() method. Or perhaps __cmp__() just shouldn't be killed off...
2006-08-23 21:41:19 -03:00
def __eq__(self, other):
return self.arg == other
class Anything:
def __eq__(self, other):
return True
def __ne__(self, other):
return False
class ComparisonTest(unittest.TestCase):
set1 = [2, 2.0, 2, 2+0j, Cmp(2.0)]
set2 = [[1], (3,), None, Empty()]
candidates = set1 + set2
def test_comparisons(self):
for a in self.candidates:
for b in self.candidates:
if ((a in self.set1) and (b in self.set1)) or a is b:
self.assertEqual(a, b)
else:
self.assertNotEqual(a, b)
def test_id_comparisons(self):
# Ensure default comparison compares id() of args
L = []
for i in range(10):
L.insert(len(L)//2, Empty())
for a in L:
for b in L:
Restructure comparison dramatically. There is no longer a default *ordering* between objects; there is only a default equality test (defined by an object being equal to itself only). Read the comment in object.c. The current implementation never uses a three-way comparison to compute a rich comparison, but it does use a rich comparison to compute a three-way comparison. I'm not quite done ripping out all the calls to PyObject_Compare/Cmp, or replacing tp_compare implementations with tp_richcompare implementations; but much of that has happened (to make most unit tests pass). The following tests still fail, because I need help deciding or understanding: test_codeop -- depends on comparing code objects test_datetime -- need Tim Peters' opinion test_marshal -- depends on comparing code objects test_mutants -- need help understanding it The problem with test_codeop and test_marshal is this: these tests compare two different code objects and expect them to be equal. Is that still a feature we'd like to support? I've temporarily removed the comparison and hash code from code objects, so they use the default (equality by pointer only) comparison. For the other two tests, run them to see for yourself. (There may be more failing test with "-u all".) A general problem with getting lots of these tests to pass is the reality that for object types that have a natural total ordering, implementing __cmp__ is much more convenient than implementing __eq__, __ne__, __lt__, and so on. Should we go back to allowing __cmp__ to provide a total ordering? Should we provide some other way to implement rich comparison with a single method override? Alex proposed a __key__() method; I've considered a __richcmp__() method. Or perhaps __cmp__() just shouldn't be killed off...
2006-08-23 21:41:19 -03:00
self.assertEqual(a == b, id(a) == id(b),
'a=%r, b=%r' % (a, b))
def test_ne_defaults_to_not_eq(self):
a = Cmp(1)
b = Cmp(1)
c = Cmp(2)
self.assertIs(a == b, True)
self.assertIs(a != b, False)
self.assertIs(a != c, True)
def test_ne_high_priority(self):
"""object.__ne__() should allow reflected __ne__() to be tried"""
calls = []
class Left:
# Inherits object.__ne__()
def __eq__(*args):
calls.append('Left.__eq__')
return NotImplemented
class Right:
def __eq__(*args):
calls.append('Right.__eq__')
return NotImplemented
def __ne__(*args):
calls.append('Right.__ne__')
return NotImplemented
Left() != Right()
self.assertSequenceEqual(calls, ['Left.__eq__', 'Right.__ne__'])
def test_ne_low_priority(self):
"""object.__ne__() should not invoke reflected __eq__()"""
calls = []
class Base:
# Inherits object.__ne__()
def __eq__(*args):
calls.append('Base.__eq__')
return NotImplemented
class Derived(Base): # Subclassing forces higher priority
def __eq__(*args):
calls.append('Derived.__eq__')
return NotImplemented
def __ne__(*args):
calls.append('Derived.__ne__')
return NotImplemented
Base() != Derived()
self.assertSequenceEqual(calls, ['Derived.__ne__', 'Base.__eq__'])
def test_other_delegation(self):
"""No default delegation between operations except __ne__()"""
ops = (
('__eq__', lambda a, b: a == b),
('__lt__', lambda a, b: a < b),
('__le__', lambda a, b: a <= b),
('__gt__', lambda a, b: a > b),
('__ge__', lambda a, b: a >= b),
)
for name, func in ops:
with self.subTest(name):
def unexpected(*args):
self.fail('Unexpected operator method called')
class C:
__ne__ = unexpected
for other, _ in ops:
if other != name:
setattr(C, other, unexpected)
if name == '__eq__':
self.assertIs(func(C(), object()), False)
else:
self.assertRaises(TypeError, func, C(), object())
def test_issue_1393(self):
x = lambda: None
self.assertEqual(x, Anything())
self.assertEqual(Anything(), x)
y = object()
self.assertEqual(y, Anything())
self.assertEqual(Anything(), y)
if __name__ == '__main__':
unittest.main()