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

[obeeker]

"""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>')

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