what's the effect of cmp here?

[levi nie]

what's the effect of cmp here? The bList and cList is the same at last.

code:
aList=[3,2,5,4]

bList=aList[:]
bList.sort()
print "bList is",bList

cList=aList[:]
cList.sort(cmp)
print "cList is",cList
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