python中一些有意思的东西

a=3;b=3
print a is b                 #True
print a+3 is b+3             #True
print a+300 is b+300         #False

print type([])               #<type 'list'>
print type(())               #<type 'tuple'>
print type(([]))             #<type 'list'>
print type(([(())]))         #<type 'list'>

c = d = 4; c *= 4
print c is d                 #False
e = f = [4]; e *= 4
print e is f                 #True

print type({():()})          #<type 'dict'>
print type({[]:[]})          #TypeError: unhashable type: 'list'