Which is the best way to extend a dictionary with another one? For instance:

>>> a = { "a" : 1, "b" : 2 }

>>> b = { "c" : 3, "d" : 4 }

>>> a

{'a': 1, 'b': 2}

>>> b

{'c': 3, 'd': 4}

I'm looking for an operation to obtain this avoiding for loop:

{ "a" : 1, "b" : 2, "c" : 3, "d" : 4 }

I wish to do something like:

a.extend(b) # This does not work