comparison with None

[Steven Howe]

Steven D'Aprano wrote:
> On Thu, 19 Apr 2007 08:18:30 -0400, Steve Holden wrote:
>
>   
>>> Which is why I suggested using the explicit type(x) == types.NoneType as 
>>> opposed to
>>> x is None
>>>
>>>
>>>       
>> This seems to go entirely against the spirit of the language. It's about 
>> as sensible as writing
>>
>>    (3 > 4) == True
>>     
>
>
> Please! For extra certainty, you should write that as:
>
> ((int(3) > int(4)) == True) == True
>
> Explicit is better than sensible, yes?
>
> *wink*
>
>
>
>   
Your example, even with the *wink*, is stupid. The language requires 3 
to be an integer, 4 to be an integer.


The point I was show is with respect to a returned variable (like from a 
function or method? *wink* *wink*).
For example, if you expect an open file handle, but get a NoneType 
because you didn't really open a file (having given a bad name or maybe 
didn't have permission to open a file), then it would be best to test 
the type of return object before using it. Then you program could handle 
the error gracefully (*wink* *wink* *wink*).

As much as I love Python, it's ability to morph an object type can be a 
pain. Testing before using can prevent a program from Error-ing out.

Steven Howe
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