list comprehension problem
Steven D'Aprano
steve at REMOVE-THIS-cybersource.com.au
Fri Oct 30 00:28:14 EDT 2009
On Thu, 29 Oct 2009 23:10:39 -0400, Nick Stinemates wrote:
>> Some objects are singletons, ie there's only ever one of them. The most
>> common singleton is None. In virtually every other case you should be
>> using "==" and "!=".
>
> Please correct me if I am wrong, but I believe you meant to say some
> objects are immutable, in which case you would be correct.
No, being immutable does not imply there is only one of it. Strings and
ints are immutable:
>>> a = 987654
>>> b = 987654
>>> a == b
True
>>> a is b
False
However, None, True, False, NotImplemented, and most (all?) builtin
functions are singletons:
>>> f = len; g = len
>>> f is g
True
>>> x = None; y = None
>>> x is y
True
--
Steven
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