python error 1.1

python filetransfer.py 0 4294967296 /Volumes/Backup\ Drive/chris/Desktop/Recording\ Sessions/S1/Session\ 1/untitled ~/Desktop/temp
  File "filetransfer.py", line 13
    with open(source, 'rb') as source_file, open(target, mode) as target_file:
                                          ^
SyntaxError: invalid syntax