William O'Higgins Witteman wrote:
> On Wed, Sep 13, 2006 at 11:34:25AM -0400, Kent Johnson wrote:
>> William O'Higgins Witteman wrote:
>>> I have to walk a directory tree and examine files within it. I have a
>>> set of directory names and filename patterns that I must skip while
>>> doing this walk. How do I create a set of rules to skip files or
>>> directory branches? I'm looking for something reasonably scalable,
>>> 'cause I'm sure to need to update these rules in the future.
>
> First, thanks to Kent and Dave for their thoughts - a big help and much
> appreciated. Notes and results below, for archival posterity (so at
> least *I'll* know where to look for it :-)
>
>> def matchesAny(name, tests):
>> for test in tests:
>> if fnmatch.fnmatch(name, test):
>> return True
>> return False
>
> fnmatch was a good choice for this in my case, because I have to do
> case-insensitive matching of very simple patterns, but re or glob would
> provide more power if needed.
> I originally put the return False inside
> the conditional with else - but that meant that unless my name matched
> on the last test in tests, it would always return False. Not what I
> wanted. The above works very nicely without the return False line.
If you leave out the return False you get an implicit return None. None
is interpreted as False in a conditional so it has the same result. I
would prefer to make it explicit.
>
>> for dirpath, dirnames, filenames in os.walk(baseDir):
>> # Note use of slice assignment - you have to modify the caller's list
>> dirnames[:] = [ name for name in dirnames if not matchesAny(name,
>> dirsToSkip) ]
>>
>> filenames = [name for name in filenames if not matchesAny(name,
>> filesToSkip) ]
>>
>> for name in filenames:
>> # whatever file processing you want to do goes here
>
> The above approach was not quite what I needed, because I had a list of
> exclusion criteria and a list of inclusion criteria, but both could be
> applied to the whole path. Therefore, I used this approach:
>
> for dirpath, dirnames, filenames in os.walk(fs_path):
> """Filter the list of filenames to exclude elements in ToSkip"""
> filenames[:] = [name for name in filenames if not
> matches(os.path.join(dirpath,name),ToSkip)]
> """Filter the list of filenames to exclude elements not in ToKeep"""
> filenames[:] = [name for name in filenames if
> matches(os.path.join(dirpath,name),ToKeep)]
>
> for fname in filenames:
> # do what needs to be done
Another way to write this that might be a little easier to read is this:
for fname in filenames:
if matches(os.path.join(dirpath,name),ToSkip):
continue
if not matches(os.path.join(dirpath,name),ToKeep):
continue
# process the file
or even
if matches(os.path.join(dirpath,name),ToSkip) or not
matches(os.path.join(dirpath,name),ToKeep):
continue
>
> This is getting me just the results I was looking for, and I have to
> say, I'm pretty pleased. Thanks again.
Python rocks :-)
Kent
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