[Tutor] Good Taste Question: Using SQLite3 in Python

[Roel Schroeven]

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