[Python-ideas] "While" suggestion

[George Sakkis]

On Thu, Jul 3, 2008 at 10:06 AM, Stavros Korokithakis <
stavros at korokithakis.net> 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.



There is already an idiom for this, although admittedly not obvious or
well-known:

for data in iter(lambda: my_file.read(1024), ''):
    do_something(data)

or in 2.5+:

from functools import partial
for data in iter(partial(my_file.read,1024), ''):
    do_something(data)

George
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