[Python-ideas] Warning on conditionals

[Amber Yust]

A better check might be to look for cases where both (a) and/or are used in
a condition and (b) the right-hand side of the and/or is a constant.

On Tue Dec 17 2013 at 7:15:06 AM, MRAB <python at mrabarnett.plus.com> wrote:

> On 17/12/2013 13:46, Peter Otten wrote:
> > f p wrote:
> >
> >> Hi, I'm new here,
> >>
> >> There are cases of bad use of int or str constants without comparison
> >> operators in the if statement as shown in this example:
> >>
> >> http://stackoverflow.com/questions/20633818/python-if-elif-always-not-
> > working.
> >>
> >> Maybe the case in which the if statement is defeated should rate a
> >> warning.
> >
> > When a newbie writes
> >
> > if animal == "cat" or "dog":
> >      ...
> >
> > it is clear that he has the wrong idea about how this is evaluated, but
> in
> > the general case
> >
> > if animal == cat or animal_barks:
> >      ...
> >
> > this is not an error. A check would be of very limited use.
> > That said, there is an external tool that issues a warning:
> >
> > $ cat tmp.py
> > import random
> > a = random.choice("ab")
> > if a == "b" or "c":
> >      print "yes"
> > else:
> >      assert False, "unreachable"
> > $ pychecker tmp.py
> > Processing module tmp (tmp.py)...
> > yes
> >
> > Warnings...
> >
> > tmp.py:3: Using a conditional statement with a constant value (c)
> >
> It's the kind of thing that you could have in IDLE.
>
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