Regex working on regexpal but not with Python

Question

I am trying to write a regex to catch email Ids . Testing since quite a few hours using regexpal.com . On the site, its able to catch all the email Ids. WHen I am substituting the same regex in Python and doing re.findall(pattern,line), it is not able to catch it.

Regex :

[a-zA-Z0-9-_]+[(.)?a-zA-Z0-9-_]*\s*(@|at)\s*[a-zA-Z0-9-_]+\s*(.|dot)\s*[a-zA-Z0-9-_]*\s*(.|dot)\s*e(\-)?d(\-)?u(\-)?(.,)?

Example :

Line =    <TR> <TD><B>E-Mail: </B> <TD><A HREF=MailTo:*[email protected]*\>*[email protected]*</A>

(Highlighted correctly on regexpal.com).

With Python :

 for line in f:
    print 'Line = ',line
        matches = re.findall(my_first_pat,line)
    print 'Matches = ',matches

Gives output:

Line =    <TR> <TD><B>E-Mail: </B> <TD><A HREF=MailTo:[email protected]>[email protected]</A>

Matches =  [('@', 'd', '.', '', '', '', ''), ('@', 'd', '.', '', '', '', '')]

What is the issue ?

BrenBarn · Accepted Answer · 2012-07-26 07:05:31Z

1

Read the documentation for re.findall:

If one or more groups are present in the pattern, return a list of groups

Your groups only capture the at sign, dot, etc., therefore that's all that's returned by re.findall. Either use non-capturing groups, wrap the whole thing in a group, or use re.finditer.

(As noted by @Igor Chubin, your regex is also incorrectly using . instead of \., but this isn't causing the main problem.)

answered Jul 26, 2012 at 7:05

BrenBarn

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2 Comments

crazyaboutliv Over a year ago

Can you explain how do I use non-capturing groups or , wrap the whole thing in a group?

BrenBarn Over a year ago

For info on that, check out just about any regex tutorial or reference, for instance regular-expressions.info .

Igor Chubin · Accepted Answer · 2012-07-26 09:13:25Z

0

You must use \. not . here:

(.|dot)

If you just want to say that you can have hyphens between letters in the edu part, you can do this without slashes and grouping:

e-?d-?u-?[.,]?

If you use () just to group symbols (but not for capturing), you must use (?:)instead:

(?:@|at)

edited Jul 26, 2012 at 9:13

answered Jul 26, 2012 at 7:04

Igor Chubin

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1 Comment

crazyaboutliv Over a year ago

This e(\-)? , I Used it in case an email is of the form [email protected] .

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