On Mon, Dec 8, 2014 at 1:24 PM, Ian Cordasco <graffatcolmin...@gmail.com>
wrote:
>
> On Dec 8, 2014 12:17 PM, "Skip Montanaro" <skip.montan...@gmail.com>
> wrote:
> >
> > Using the same variable in nested loops within the same function seems
> at least as serious as a shadowed global (or builtin) name.
>
> I agree. I think this belongs in PyFlakes (as far as flake8 is concerned)
> but Phil may disagree.
>
Maybe. As a matter of principle, Pyflakes should only emit a warning for
things that it is sure is an error.
Currently, pyflakes only emits a warning if you redefine an import without
ever using it. For example:
import x
def f():
x = 2
print x
<stdin>:1: 'x' imported but unused
<stdin>:3: redefinition of unused 'x' from line 1
It does not do this for other kinds of definitions:
x = 1
def f():
x = 2
print x
[no errors]
Also note that as long as the imported "x" is used somewhere, then there
are no warnings, even if "x" is shadowed in some scopes:
import x
def f():
x = 2
print x
def g():
print x
[no errors]
The reasoning here is that if you import a thing and then redefine it
without using it ever, that's just the same as importing a thing and not
using it.
However, I can come up with use cases for shadowing variables from function
scope or in nested loops. For example, event-based libraries frequently
expect callbacks that take one parameter which the callback may or may not
care about. Or, we may use a for loop to do something a number of times
without caring about the iteration count. I tend to use "_" for these sorts
of things, a convention I got from lisp.
def thingHappened(_):
# don't care about the thing that happened, just that it happened
class Sheldon:
def visit_penny(self):
for _ in xrange(3):
for _ in xrange(3):
knock()
say('penny')
I wouldn't want a warning in these cases, as they are legitimate and
correct. Can you think of any additional reasoning we could apply that
would catch your case, but not these?
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