Python implements the method of merging two dictionaries (dict)

This article provides an example of how two dictionaries (dict) can be merged in Python. Specific methods are as follows:

There are two dictionaries dict as follows:

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

Merging the two dictionaries results in something like:

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

Method 1:

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

Method 2:

dictMerged2=dict(dict1, **dict2)

Method 2 is equivalent to:

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

Or:

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

Method 2 is much faster than method 1 and is tested with timeit as follows

$ 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

I hope this article has helped you with your Python programming.