How to use python regular expression to substitute string value

[Pasi Savolainen]

Allerdyce.John at gmail.com writes:

> When I try your idea, I have this error
>
>     x, y, width, height = re.findall(pattern, str)[0]
> IndexError: list index out of range
>
> How can I use findall to handle error case? i.e. what if there is no
> match? how can I handle it gracefully?

This is explained in python docs, and do try them in interactive python,
for example IPython is great for this stuff.

- -
ipython ->

In [1]:import re 

In [2]:line = "foobar"

In [3]:re.findall ("baz", line)
Out[3]:[]

In [4]:re.findall ("o", line)
Out[4]:['o', 'o']
- -

So you can do:
- -
match = re.findall(pattern, str)
if match:
   x, y, width, height = match[0]
   ...
else:
   # no match
- -



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   Psi -- <http://www.iki.fi/pasi.savolainen>