zip function for python

[Luca]

Hi, Ive written this easy and fast function cause there it was
impossible for me to find one that zip a directory without external
libraries:

import zipfile
import sys
import os

def zipdir(zipPath,directory="./"):
"""Store the cdontent of directory to a zipPath file, if directory is
not given stores the content of the current dir
( lu*************@gmail.com )"""
directory=os.path.realpath(directory)
zipObject = zipfile.ZipFile(zipPath, 'w')
for root, dirs, files in os.walk(directory):
for file in files:
arcfile=root[len(os.path.commonprefix((directory, root)))
+1:]+"/"+file #retrieves the inner relative file path
filepath=os.path.join(root,file)
zipObject.write(filepath,arcfile)
zipObject.close()
return zipObject #for optional further elaborations