Coding style

[Carl Banks]

Patrick Maupin wrote:
> PTY wrote:
>
> > It looks like there are two crowds, terse and verbose.  I thought terse
> > is perl style and verbose is python style.  BTW, lst = [] was not what
> > I was interested in :-)  I was asking whether it was better style to
> > use len() or not.
>
> It's not canonical Python to use len() in this case.  From PEP 8:
>
> - For sequences, (strings, lists, tuples), use the fact that empty
>       sequences are false.
>
>       Yes: if not seq:
>            if seq:
>
>       No: if len(seq)
>           if not len(seq)
>
> The whole reason that a sequence supports testing is exactly for this
> scenario.  This is not an afterthought -- it's a fundamental design
> decision of the language.

That might have made sense when Python and string, list, tuple were the
only sequence types around.

Nowadays, Python has all kinds of spiffy types like numpy arrays,
interators, generators, etc., for which "empty sequence is false" just
doesn't make sense.  If Python had been designed with these types in
mind, I'm not sure "empty list is false" would have been part of the
language, let alone recommend practice.


Carl Banks