Trying to use Python context managers and streams together, but it doesn't work

VisitDirs.py

import os, sys
from contextlib import contextmanager
from glob import glob

@contextmanager
def visitDir(d):
    os.chdir(d)
    yield d
    os.chdir("..")

paths = [os.path.join('.', p[0:-1]) for p in glob('*/')]

def clean():
    for p in (visitDir(p) for p in paths): # This is the magic line
        print p
        print os.getcwd()

clean() # Context manager apparently expires within the generator expression