Python Backing Up a Folder into a ZIP File

# !/user/bin/env python
# - Copeies an entire folder and its contents into
# a Zip file whose filename increments.

import zipfile, os


def backupToZip(folder):
    # Backup the entire contents of ''folder' into a Zip file
    folder = os.path.abspath(folder) # make sure folder is absolute
    # Figure out the filename this code should use based on what files already exist
    number = 1
    while True:
        zipFilename = os.path.basename(folder) + '_' +str(number) + '.zip'
        if not os.path.exists(zipFilename):
            break
        number += 1
    # Create Zip file.
    print('Creating {}'.format(zipFilename))
    backupzip = zipfile.ZipFile(zipFilename, 'w')

    # Walk the enter folder tree and compress the files in each folder.
    for foldername, subfolders, filenames in os.walk(folder):
        print('adding files in {}'.format(foldername))
        # Add the current folder to the Zip file.
        backupzip.write(foldername)
        # Add all the files in this folder to the zip file
        for filename in filenames:
            newBase = os.path.basename(folder) + '_'
            if filename.startswith(newBase) and filename.endswith('.zip'):
                continue
            backupzip.write(os.path.join(foldername, filename))
    backupzip.close()
    print('done')


def main():
    backupToZip("1702")



if __name__ == '__main__':
    main()