call(['find', '/path/to/site', '-type', 'd', '-exec', 'chmod', '755', '{}', ';'])
call(['find', '/path/to/site', '-type', 'd', '|', 'xargs', 'chmod', '755'])
find: paths must precede expression: |
Usage: find [-H] [-L] [-P] [-Olevel] [-D help|tree|search|stat|rates|opt|exec] [path...] [expression]