why doesn't is work?a script to backup a directory

[obeeker at gmail.com]

"""there is threee directories,one of these is used for the base
directory,decided by the user, default is d0"""

import shutil


#the three directories
d0='D:/Program Files/eb/mb/S'
d1='O:/eb/mb/S'
d2='P:/S/eb/mb/S'

#to backup
def update(base):
	l=[d0,d1,d2]
	l.remove(base)

	for i in l:
		shutil.rmtree(i)

	for i in l:
		shutil.copytree(base,i)

#use the base directory to invoke the update() func
def updateNow(base):
	try:
		if base=='d1':
			update(d1)
		elif base=='d2':
			update(d2)
		else:
			update(d0)

	except:
		print "sth is wrong"
	else:
		print "OK!"

#promt user which is the base
if __name__ == '__main__':
	print 'd0=',d0
	print 'd1=',d1
	print 'd2=',d2
	base=raw_input("your base/standard directory is d0 d1 or d2  ?\n")
	print base
	updateNow(base)
	
	raw_input('press Return>')