[Tutor] don't understand iteration

Clayton Kirkwood crk at godblessthe.us
Tue Nov 11 01:52:57 CET 2014

>-----Original Message-----
>From: Tutor [mailto:tutor-bounces+crk=godblessthe.us at python.org] On
>Behalf Of Alan Gauld
>Sent: Monday, November 10, 2014 3:59 PM
>To: tutor at python.org
>Subject: Re: [Tutor] don't understand iteration
>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.

Good point, although a nice side effect would be an added reference like
search.matches which when accessed would return the value. It knows the
value, it just isn't being made available.

>> 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()

I'll explore

>> 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.

I believe that is true only if you are receiving a single return value. If
it is more than one group, it returns a tuple (I guess of strings).

>Alan G
>Author of the Learn to Program web site
>Tutor maillist  -  Tutor at python.org
>To unsubscribe or change subscription options:

More information about the Tutor mailing list