[Python-ideas] "While" suggestion

[Stavros Korokithakis]

I don't think they do, if I'm not mistaken the only way is to call 
read() and see if it returns the empty string. I agree that this would 
be better, but the use case I mentioned is not the only one this would 
be useful in... Unfortunately I can't think of any right now, but there 
have been a few times when I had to initialise things outside the loop 
and it always strikes me as ugly.

Thomas Lee wrote:
> It's not currently possible to determine if a file/stream is at its end, 
> is it?
> 
> If that were the case you could easily do the read before your 
> do_something call. Something like:
> 
> while not my_file.eof:
>  data = my_file.read(1024)
>  do_something(data)
> 
> Can anyone explain why file objects don't support some sort of eof 
> check? Something gives me the impression that it was an intentional 
> decision.
> 
> IMO something like this would be better than more syntax.
> 
> Cheers,
> T
> 
> Stavros Korokithakis wrote:
>> Hello all,
>> I have noticed that sometimes "while" loops produce "unpythonic" 
>> patterns, such as the following:
>>
>> data = my_file.read(1024)
>> while data:
>>     do_something(data)
>>     data = my_file.read(1024)
>>
>> The assignment is repeated, which is less than optimal. Since we don't 
>> have a while statement that does the check in the end, would it not be 
>> better if the syntax of while could be amended to  include something 
>> like this (in the spirit of the new "with" keyword)?:
>>
>> while my_file.read(1024) as data:
>>    do_something(data)
>>
>> This would terminate the loop when myfile.read() evaluated to False, 
>> and it is more pythonic than repeating onesself.
>>
>> I contacted GvR about this, and he replied that this syntax would have 
>> to be part of the expression than part of the while, which I agree 
>> would be less than ideal. However, I don't see why it would have to be 
>> part of the expression, since the "while" could easily assign the 
>> value of the expression to the variable and break if it evaluates to 
>> False.
>>
>> I would appreciate any thoughts on this,
>> Stavros Korokithakis
>> ------------------------------------------------------------------------
>>
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> 
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