Alan Gauld schreef op 2015-04-29 18:43:
On 29/04/15 17:03, Jugurtha Hadjar wrote:
http://docs.python-guide.org/en/latest/writing/style/#create-an-ignored-variable
I've seen this before and strongly disagree with it.
I disagree with your disagreement. I'll try to explain.
They are ambiguous, difficult to remember, easy to overlook
I'm not sure what exactly you mean by that.
and if you change your mind and decide you need to use it later
> it's a whole new name to go back and introduce
True, but I don't see how that is a problem. At that point the variable
is only used at one point, so you only have to rename it at that one place.
(or worse be tempted to use the meaningless symbol).
That would be bad indeed, but I think a very minimal amount of
discipline is enough to avoid that.
And if you need another 'throw-away' name later you use the same one, then
forget
> here are two uses and try to use it anyway (even in debugging) and get
completely wrong values, that may or may not look different
to what you expect.
The whole point of ignored variables is that you don't use them. If you
use them, they're not exactly ignored variables. It doesn't matter if
you use __ once or twice or many times more; all of them are to be ignored.
> (looking different is good - you can
> detect it easily, looking similar is very, very, bad!)...
> its just a horror story waiting to trip you up.
I'm not sure in what way __ can lead to horror stories. Do you have an
example to fuel my imagination?
> It's far better to have a short meaningful name that is never
> used than a bland, meaningless, generic symbol.
By 'short meaningful name', do you mean something like 'dummy' or
'ignorethis' as in
basename, dummy, ext = filename.rpartition('.')
or rather something like
basename, separator, ext = filename.rpartition('.')
In the first case, I prefer __ over dummy exactly because to me it's
clearer at a glance that the name is one-use only and the value is to be
ignored.
In the second case, using a 'real' name like 'separator' means I now
have to mentally keep track of it since as far as I can see at that
point it might be used later in the code.
To me, using _ or __ decreases the cognitive load because they tell me I
don't have to remember anything about them, since they're not going to
be used later. Read and forget.
Best regards,
Roel
--
The saddest aspect of life right now is that science gathers knowledge
faster than society gathers wisdom.
-- Isaac Asimov
Roel Schroeven
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