Iterate over text file, discarding some lines via context manager

fetchinson . fetchinson at googlemail.com
Fri Nov 28 16:44:03 CET 2014


On 11/28/14, Dave Angel <davea at davea.name> wrote:
> On 11/28/2014 10:04 AM, fetchinson . wrote:
>> Hi all,
>>
>> I have a feeling that I should solve this by a context manager but
>> since I've never used them I'm not sure what the optimal (in the
>> python sense) solution is. So basically what I do all the time is
>> this:
>>
>> for line in open( 'myfile' ):
>>      if not line:
>>          # discard empty lines
>>          continue
>>      if line.startswith( '#' ):
>>          # discard lines starting with #
>>          continue
>>      items = line.split( )
>>      if not items:
>>          # discard lines with only spaces, tabs, etc
>>          continue
>>
>>      process( items )
>>
>> You see I'd like to ignore lines which are empty, start with a #, or
>> are only white space. How would I write a context manager so that the
>> above simply becomes
>>
>> with some_tricky_stuff( 'myfile' ) as items:
>>      process( items )
>>
>
> I see what you're getting at, but a context manager is the wrong
> paradigm.  What you want is a generator.   (untested)
>
> def mygenerator(filename):
>      with open(filename) as f:
>          for line in f:
>              if not line: continue
>              if line.startswith('#'): continue
>              items = line.split()
>              if not items: continue
>              yield items
>
> Now your caller simply does:
>
> for items in mygenerator(filename):
>        process(items)

Great, thanks a lot!

Cheers,
Daniel


>
> --
> DaveA
> --
> https://mail.python.org/mailman/listinfo/python-list
>


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