Python合并两个字典

a = {1:1, 2:2}
b = {1:2, 3:3}

#way 1
print dict(a.items()+b.items())
#way 2
#fail (producing a TypeError) in Python 3.2, and in current versions of Jython, PyPy and IronPython: for those versions of Python, when passing a dict with the ** notation, all the keys of that dict should be strings.
print dict(a, **b) 
#way 3
c = a.copy()
c.update(b)
print c