None in string => TypeError?
Roy Smith
roy at panix.com
Mon Jun 9 11:34:42 EDT 2014
We noticed recently that:
>>> None in 'foo'
raises (at least in Python 2.7)
TypeError: 'in <string>' requires string as left operand, not NoneType
This is surprising. The description of the 'in' operatator is, 'True if an item of s is equal to x, else False '. From that, I would assume it behaves as if it were written:
for item in iterable:
if item == x:
return True
else:
return False
why the extra type check for str.__contains__()? That seems very unpythonic. Duck typing, and all that.
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