Excluding directories in os.walk

Modifying dirs in-place will prune the (subsequent) files and directories visited by os.walk:

# exclude = set(['New folder', 'Windows', 'Desktop'])
for root, dirs, files in os.walk(top, topdown=True):
    dirs[:] = [d for d in dirs if d not in exclude]

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From help(os.walk):

When topdown is true, the caller can modify the dirnames list in-place (e.g., via del or slice assignment), and walk will only recurse into the subdirectories whose names remain in dirnames; this can be used to prune the search...

... an alternative form of @unutbu's excellent answer that reads a little more directly, given that the intent is to exclude directories, at the cost of O(n**2) vs O(n) time.

(Making a copy of the dirs list with list(dirs) is required for correct execution)

# exclude = set([...])
for root, dirs, files in os.walk(top, topdown=True):
    [dirs.remove(d) for d in list(dirs) if d in exclude]