[Python-ideas] if condition: break idiom

[Brett Cannon]

On Sat, Sep 20, 2008 at 11:35 AM, Arnaud Delobelle
<arnodel at googlemail.com> wrote:
> Hello,
>
> It seems to me that a lot of the time that I use a break statement, it is
> directly after an if.  Typically:
>
> while True:
>    do something
>    if condition:
>        break
>    do something else
>
> I don't like so much the if .. break which is spread over two lines.  Of
> course I could write
>
> while True:
>    do something
>    if condition: break
>    do something else
>
> It doesn't read so well either IMHO. I think that this would look better:
>
> while True:
>    do something
>    break if condition
>    do something else
>

For some reason this suggestion reminds me of Icon.

Anyway, so I take it this suggestion is to extend the break statement
to have an 'if' trailer? Or are you trying to make 'break' an
expression?

If you are after the former, the problem with that is that the
special-casing of 'if' might confuse people because they will suddenly
want an 'else' clause. Adding that might then cause a naive user to
see ``break if x`` and then think 'break' is an expression.

Which leads to its own issues. How do you implement 'break' as an
expression? It doesn't make much sense to have ``fxn(a, break, b)``
inside a loop. And you can't say 'break' can only appear in the true
clause of an 'if' expression as that is too specialized and will lead
to potential misuse of the statement (or at least an attempt).

I don't see enough benefit from the change to warrant dealing with any
of the above issues.

-Brett