python中两个字典（dict）合并

dict1={1:[1,11,111],2:[2,22,222]}
dict2={3:[3,33,333],4:[4,44,444]}

合并两个字典得到类似 {1:[1,11,111],2:[2,22,222],3:[3,33,333],4:[4,44,444]}

方法一：

dictMerged1=dict(dict1.items()+dict2.items())

方法二：

dictMerged2=dict(dict1, **dict2)

方法2等同于：

dictMerged=dict1.copy()
dictMerged.update(dict2)

或者

dictMerged=dict(dict1)
dictMerged.update(dict2)

方法2比方法1速度快很多，用timeit测试如下

$ python -m timeit -s 'dict1=dict2=dict((i,i) for i in range(100))' 'dictMerged1=dict(dict1.items()+dict2.items())'

10000 loops, best of 3: 20.7 usec per loop



$ python -m timeit -s 'dict1=dict2=dict((i,i) for i in range(100))' 'dictMerged2=dict(dict1,**dict2)'

100000 loops, best of 3: 6.94 usec per loop



$ python -m timeit -s 'dict1=dict2=dict((i,i) for i in range(100))' 'dictMerged3=dict(dict1)' 'dictMerged3.update(dict2)'

100000 loops, best of 3: 7.09 usec per loop



$ python -m timeit -s 'dict1=dict2=dict((i,i) for i in range(100))' 'dictMerged4=dict1.copy()' 'dictMerged4.update(dict2)'

100000 loops, best of 3: 6.73 usec per loop