if <assignment>:

[David Brown]

"André Næss" <andre.hates.spam at ifi.uio.no> wrote in message
news:arqm0r$s6f$1 at maud.ifi.uio.no...
> When I started learning Python one of the things that surprised me was
that
> you couldn't do assignments inside the if clause, e.g.:
>
> if myvar = someFunction():
>
> My question is, what is the rationale for this? Is it a technical issue?
Or
> purely a matter of language design? I'm curious because I'm interested in
> the design og programming languages, not because I want this behavior
> changed in Pyton :)
>
> Thanks.
> André Næss
>

My guess is that the languages you are most familiar with are C and C++.
The question should not be "why doesn't Python support 'if myvar =
someFunc()'?", but "why *does* C support 'if (myvar = someFunc())' ?"  The
answer is that C was designed with the sole aim of reducing keystrokes for
the programmer, regardless of its effect on program readability and
correctness.  This particular "feature" is a huge source of bugs and
frustration in C programming - mixing up "=" and "==" in conditions is
probably the biggest single cause of C program bugs.  Python, on the other
hand, is designed for improving program readability and correctness, even if
it occasionally (actually seldom in practice) requires more keystrokes.