Unzip a file in python - note that extractall() is sensible to traversal attacks

Unzip file

import zipfile,os.path
def unzip(source_filename, dest_dir):
    with zipfile.ZipFile(source_filename) as zf:
        for member in zf.infolist():
            # Path traversal defense copied from
            # http://hg.python.org/cpython/file/tip/Lib/http/server.py#l789
            words = member.filename.split('/')
            path = dest_dir
            for word in words[:-1]:
                drive, word = os.path.splitdrive(word)
                head, word = os.path.split(word)
                if word in (os.curdir, os.pardir, ''): continue
                path = os.path.join(path, word)
            zf.extract(member, path)