PEP 276 (was Re: Status of PEP's?)

[Bernhard Herzog]

James_Althoff at i2.com writes:

> [Aahz Maruch]
> > My primary complaint about the PEP is that the following idiom is
> > awkward, ugly, and prone to misunderstanding:
> >
> >   if i in 5:
> 
> I will note this.
> 
> However given that current Python seems able to do type-checking on strings
> used with "in" as in, for example:
> 
> >>> 1 in 'spam'
> Traceback (most recent call last):
>   File "<stdin>", line 1, in ?
> TypeError: 'in <string>' requires character as left operand
> >>>

That's because strings implement the in operator. However, Python is
smart enough to make in work for iterable objects. Quick experiment
(Python 2.2):

>>> from __future__ import generators
>>> class MyInt(int):
...      def __iter__(self):
...             for i in range(self):
...                      yield i
... 
>>> num = MyInt(3)
>>> for i in num: print i
... 
0
1
2
>>> 1 in num
1



   Bernhard

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