help with simple script and strings

I'm just getting started with python. Curious what I need to change to properly filter out only strings starting with "200" script: #!/usr/bin/python directories = ['20080412', '20080324', 'blahblah', 'latest-dir', 'rawhide-20080410', 'rawhide-20080411', 'rawhide-20080412' , '20080401'] print 'directories == %s' % directories for directory in directories: print 'processing directory %s ' % directory if not directory.startswith('200'): directories.remove(directory) print 'removed == %s' % directory print 'directories == %s' % directories ~~~~~~~~~~~~~~~~~~~~~~~~~ output: $ python dir-filter.py directories == ['20080412', '20080324', 'blahblah', 'latest-dir', 'rawhide-20080410', 'rawhide-20080411', 'rawhide-20080412', '20080401'] processing directory 20080412 type == <type 'str'> processing directory 20080324 type == <type 'str'> processing directory blahblah type == <type 'str'> removed == blahblah processing directory rawhide-20080410 type == <type 'str'> removed == rawhide-20080410 processing directory rawhide-20080412 type == <type 'str'> removed == rawhide-20080412 directories == ['20080412', '20080324', 'latest-dir', 'rawhide-20080411', '20080401'] ~~~~~~~~~~~~~~~~~~~~ why do 'rawhide-20080411' and 'latest-dir' remain? Thanks, John