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From: Chris Angelico <rosuav@gmail.com>
Newsgroups: comp.lang.python
Subject: Re: Regex: Perl to Python
Date: Mon, 7 Mar 2016 15:45:26 +1100
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On Mon, Mar 7, 2016 at 3:38 PM, Fillmore <fillmore_remove@hotmail.com> wrote:
> pattern = re.compile(r"(\d+)\t(.+)$")
> with open(fields_Indexfile,mode="rt",encoding='utf-8') as headerfile:
>     for line in headerfile:
>         #sys.stdout.write(line)
>         m = pattern.match(line)
>         print(m.group(0))
>     headerfile.close()
>
> but I must be getting something fundamentally wrong because:
>
> Traceback (most recent call last):
>   File "./slicer.py", line 30, in <module>
>     print(m.group(0))
> AttributeError: 'NoneType' object has no attribute 'group'
>
>
>  why is 'm' a None?

When the regex doesn't match, Python gives you back None instead of a
match object. Your Perl code has an 'if' to guard that; you can do the
same thing:

if m:
    print(m.group(0))

ChrisA