Unwanted behaviour from dict.fromkeys

Question

I\'d like to initialise a dictionary of sets (in Python 2.6) using dict.fromkeys, but the resulting structure behaves strangely. More specifically:

Answer 1

#To do what you want:

import copy
s = set([])
x = {}
for n in range(0,5):
  x[n] = copy.deepcopy(s)
x[2].add(3)
print x

#Printing
#{0: set([]), 1: set([]), 2: set([3]), 3: set([]), 4: set([])}