[Python-ideas] Please reconsider the Boolean evaluation of midnight

[M.-A. Lemburg]

On 06.03.2014 12:09, Antoine Pitrou wrote:
> Le 06/03/2014 12:04, M.-A. Lemburg a écrit :
>>
>> Writing
>>
>>      if x: print ('x is None')
>>
>> or
>>
>>      if x == None: print ('x is None')
>>
>> is wrong code.
> 
> No it isn't.
> 
>> None is a singleton, so you have to use the "is" operator, i.e.
>>
>>      if x is None: print ('x is None')
>>
>> is the only correct way of testing for None.
> 
> No it isn't.  x == None is a perfectly well-defined way of doing it, even if it isn't the
> stylistically preferred one.

Depends on what kind of type x is and how that type implements
the comparison slots. It is perfectly well possible to define a
type that returns True for (x == None), even though x is not None :-)

>>> class C:
...     def __eq__(self, other):
...         return (other is None)
...
>>> o = C()
>>> o == None
True

-- 
Marc-Andre Lemburg
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