[Tutor] don't understand iteration

Alan Gauld alan.gauld at btinternet.com
Tue Nov 11 00:58:35 CET 2014

On 10/11/14 23:08, Clayton Kirkwood wrote:

>>> I couldn't find a way to get the len of blah.
>> What would you expect the answer to be?
> I would expect len(sizeof, whatever)(blah) to return the number of (in this
> case) matches, so 5.

But remember that search is matching the pattern, not the groups - 
that's a side effect. So len(matchObject) could just as validly
return the length of the string that matched the pattern.
It just depends on the content that you are using.

> of matches. Why else would you do a search

To look for a pattern. I very rarely use groups in regex - and
I try not to use regex at all! If I can find the matching substring
I will likely be able to pull out the details using regular string 
methods or other tools. For example in your case I might have tried 
using time.strparse()

> certainly wouldn't want len(group) to return the number of characters, in
> this case, 28 (which it does:>{{{

But group() - with default group of 0 - returns the whole matched 
substring and len() on a string returns the number of characters.
You want len(match.groups()) to get the number of matches.

> I didn't run group to find out the number of characters in a string, I ran
> it to find out something about blah and its matches.

But group() - singular - returns a single group item which is always a 
string. You use group() to get the matching substring. You use groups to 
find all the substrings.

Alan G
Author of the Learn to Program web site

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