shutil.copytree small improvement

When you have to work with directories and files, there's a very common pattern: copying a directory into another, but filtering out a few files and directories.

For instance, if you want to copy a directory that contains source code, you will probably remove .pyc files and .svn directories if you work with Subversion. In that case, shutil.copytree cannot be used, so os.walk is the usual way to go (rough example):
import os

from os.path import join, splitext, split, exists

from shutil import copyfile



def copy_directory(source, target):

    if not os.path.exists(target):

        os.mkdir(target)

    for root, dirs, files in os.walk(source):

        if '.svn' in dirs:

            dirs.remove('.svn')  # don't visit .svn directories

        for file in files:

            if splitext(file)[-1] in ('.pyc', '.pyo', '.fs'):

                continue

            from_ = join(root, file)

            to_ = from_.replace(source, target, 1)

            to_directory = split(to_)[0]

            if not exists(to_directory):

                os.makedirs(to_directory)

            copyfile(from_, to_)

This is a lot of boiler-plate code, so I usually create a small function that accepts more arguments to filter out files and directory. But Python should provide this pattern in the standard library.

I have proposed a patch for shutil.copytree, to integrate filtering capability. It has been reviewed and commited in the trunk this week, so we will have it in Python 2.6. Now copytree comes with an ignore argument that has to be a callable. If given it will be called on each visited directory to decide what is copied and what is not.

There's a default callable in shutil called ignore_patterns, that can be used to filter out files with glob-style patterns. I have added this example to Python doc:
from shutil import copytree, ignore_patterns

copytree(source, destination, ignore=ignore_patterns('*.pyc', 'tmp*'))

Pretty straight forward ! :D
More info and examples here : [http://docs.python.org/dev/library/shutil.html#shutil.copytree][]

Comments !