class foo(list):
def __eq__(self, other):
raise 'foo.__eq__ called'
>>> help(list.__eq__)
Help on wrapper_descriptor:
__eq__(...)
x.__eq__(y) <==> x==y
>>> [].__eq__(foo())
True
>>> [] == foo()
Traceback (most recent call last):
File "", line 1, in ?
File "", line 3, in __eq__
foo.__eq__ called
Help says those two statements should be equivalent. Why aren't they?
Comments
foo() == []
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frafr jura lbh guvax nobhg ubj lbh'q hfhnyyl hfr fhoglcrf va guvf jnl.
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class hat( object ):
def __eq__(self , other ):
print "I am hat"
print "other is a %s" % ( other.__class__.__name__ )
return True
class tree( object ):
def __eq__(self , other ):
print "I am tree"
print "other is a %s" % ( other.__class__.__name__ )
return False
a = hat()
b = tree()
a == b
b == a
it prints:
I am hat
other is a tree
I am tree
other is a hat
class hat( object ):
def __eq__(self , other ):
return NotImplemented
class tree( object ):
def __eq__(self , other ):
print "I am tree"
print "other is a %s" % ( other.__class__.__name__ )
return True
a = hat()
b = tree()
a == b
b == a
returns:
I am tree
other is a hat
I am tree
other is a hat
The NotImplemented forces it to try the other available __eq__()
...
Sorry. Had to.