Iterate over text file, discarding some lines via context manager
Dave Angel
davea at davea.name
Fri Nov 28 10:22:18 EST 2014
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)
--
DaveA
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