Remove empty strings from list

[Rhodri James]

On Tue, 15 Sep 2009 02:55:13 +0100, Chris Rebert <clp2 at rebertia.com> wrote:

> On Mon, Sep 14, 2009 at 6:49 PM, Helvin <helvinlui at gmail.com> wrote:
>> Hi,
>>
>> Sorry I did not want to bother the group, but I really do not
>> understand this seeming trivial problem.
>> I am reading from a textfile, where each line has 2 values, with
>> spaces before and between the values.
>> I would like to read in these values, but of course, I don't want the
>> whitespaces between them.
>> I have looked at documentation, and how strings and lists work, but I
>> cannot understand the behaviour of the following:
>>                        line = f.readline()
>>                        line = line.lstrip() # take away whitespace at  
>> the beginning of the
>> readline.
>>                        list = line.split(' ') # split the str line into  
>> a list
>>
>>                        # the list has empty strings in it, so now,
>> remove these empty strings
[snip]
>
> Block quoting from http://effbot.org/zone/python-list.htm
> """
> Note that the for-in statement maintains an internal index, which is
> incremented for each loop iteration. This means that if you modify the
> list you’re looping over, the indexes will get out of sync, and you
> may end up skipping over items, or process the same item multiple
> times.
> """
>
> Thus why your code is skipping over some elements and not removing them.
> Moral: Don't modify a list while iterating over it. Use the loop to
> create a separate, new list from the old one instead.

In this case, your life would be improved by using

	l = line.split()

instead of

	l = line.split(' ')

and not getting the empty strings in the first place.

-- 
Rhodri James *-* Wildebeest Herder to the Masses