which is more 'pythonic' / 'better' ?

[Steven D'Aprano]

On Mon, 12 Sep 2005 12:52:52 +0200, gabor wrote:

> hi,
> 
> there are 2 versions of a simple code.
> which is preferred?
> 
> 
> ===
> if len(line) >= (n+1):
> 	text = line[n]
> else:
> 	text = 'nothing'
> ===
> 
> 
> ===
> try:
> 	text = line[n]
> except IndexError:
> 	text = 'nothing'
> ===
> 
> 
> which is the one you would use?

Personally, I would use either. You say po-ta-to, I say pot-at-o.

try...except... blocks are quick to set up, but slow to catch the
exception. If you expect that most of your attempts will succeed, then the
try block will usually be faster than testing the length of the list
each time.

But if you expect that the attempts to write the line will fail more
frequently, then testing will be quicker.

You will need to do your own testing before hand to find the exact
cut-off, and expect that cut-off to vary according to the Python
implementation and version. But a rough rule of thumb is, if you expect
your code to fail more often than succeed, then test first, otherwise
catch an exception.



-- 
Steven.