[Python-ideas] BUG in standard while statement

Chris Barker chris.barker at noaa.gov
Fri Sep 11 01:05:43 CEST 2015

On Thu, Sep 10, 2015 at 3:12 PM, MRAB <python at mrabarnett.plus.com> wrote:

> You could use a generator expression with a function that discards the
> results:
> def every(iterable):
>     for _ in iterable:
>         pass
> every(obj.a_method() for obj in a_sequence)

sure -- though this adds a new function that people reading my code need to

Andrew Barnert wrote:

> > [obj.a_method() for obj in a_sequence]

I think this is an anti-pattern. The point of a comprehension is that it's
> an expression, which gathers up results. You're trying to hide side effects
> inside an expression, which is a bad thing to do, and lamenting the fact
> that you get a useless value back, which of course you do because
> expressions have values, so that should be a sign that you don't actually
> want an expression here.

Exactly -- I don't want a comprehension, I don't want a expression, I want
a concise way to spell : do this thing to all of these things....

Also, compare the actual brevity here:
>     [obj.a_method() for obj in a_sequence]
>     for obj in a_sequence: obj.a_method()
> You've replaced a colon with a pair of brackets, so it's actually less
> concise.

Fair enough -- removing a newline does make that pretty simple looking!

I guess I got all comprehension-happy there -- back when it was the shiny
new toy, and then I got stuck on it.



Christopher Barker, Ph.D.

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Chris.Barker at noaa.gov
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