Comparison of efficiency examples of merging two dictionaries in Python

This article mainly introduces the common methods and efficiency comparison of Python. It analyzes and compares the common methods of merging dictionaries in Python. Friends who need it can refer to it

The example in this article describes the common methods and efficiency comparison of merging two dictionaries in Python. Share it with everyone for your reference. The specific analysis is as follows:

The following code illustrates 5 methods of merging two dictionaries, and conducts a simple performance test

#!/usr/bin/python 
import time 
def f1(d1, d2): 
  return dict(d1, **d2) 
def f2(d1, d2): 
  return dict(d1.items() + d2.items()) 
def f3(d1, d2): 
  d = d1.copy() 
  d.update(d2) 
  return d 
def f4(d1, d2): 
  d1.update(d2) 
  return d1 
def f5(d1, d2): 
  d = dict(d1) 
  d.update(d2) 
  return d 
def f6(d1, d2): 
  return (lambda a, b: (lambda a_copy: a_copy.update(b) or a_copy)(a.copy()))(d1, d2) 
def f7(d1, d2): 
  d = {} 
  d.update(d1) 
  d.update(d2) 
  return d 
def t(f, n): 
  st = time.time() 
  for i in range(1000000): 
    dic1 = {'a':'AA','b':'BB','c':'CC'} 
    dic2 = {'A':'aa','B':'bb','C':'cc'} 
    f(dic1, dic2) 
  et = time.time() 
  print '%s cost:%s'%(n, et-st) 
t(f1, 'f1') 
t(f2, 'f2') 
t(f3, 'f3') 
t(f4, 'f4') 
t(f5, 'f5') 
t(f6, 'f6') 
t(f7, 'f7')

Except the f4 method will cause destructive modifications to the dictionary d1 In addition, several other methods return the merged result as a new dictionary.

The following are the test results:

f1 cost:2.382999897 
f2 cost:4.45399999619 
f3 cost:3.02100014687 
f4 cost:1.73000001907 
f5 cost:2.3710000515 
f6 cost:2.89700007439 
f7 cost:2.35600018501

It can be seen that f4 is the most efficient. If you do not need to retain the original dictionary, it is recommended to use the f4 method.

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