On 2017-12-18 21:25, Tim Chase wrote:
Playing around, I had this (happens to be Py2, but gets the same
result in Py3) code
class X(object):
ONE = "one"
TWO = "two"
_ALL = frozenset(v for k,v in locals().items() if k.isupper())
@classmethod
def __contains__(cls, v):
return v in cls._ALL
print(dir(X))
print(X._ALL)
Running this gives
['ONE', 'TWO', '_ALL', '__class__', '__contains__', '__delattr__',
'__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__',
'__getattribute__', '__gt__', '__hash__', '__init__', '__le__',
'__lt__', '__module__', '__ne__', '__new__', '__reduce__',
'__reduce_ex__', '__repr__', '__setattr__', '__sizeof__',
'__str__', '__subclasshook__', '__weakref__']
And then, depending on whether it's Py2 or Py3, I get either
frozenset({'one', 'two'})
frozenset(['two', 'one'])
Which I expect. Hey, look. There's a __contains__ method. And it
has been specified as a @classmethod. So I want to test it:
print("one" in X)
However that fails with
Traceback (most recent call last):
File "x.py", line 10, in <module>
print("one" in X)
TypeError: argument of type 'type' is not iterable
My understanding was that "in" makes use of an available __contains__
but something seems to preventing Python from finding that.
What's going on here?
Maybe it's just because it's intended to be an instance method, like
__getitem__.
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