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python列表推导 和 内置函数map,filter 效率对比

2012-03-08

前言在python中的列表操作主要有两种,一种类似于lisp的函数编程方法:filter( function,list) , map( function, list)另一种特别pythonic——列表推导 [ i for i in list ]现在就两种方法进行对比,...

前言
在python中的列表操作主要有两种,
一种类似于lisp的函数编程方法:filter( function,list) , map( function, list)
另一种特别pythonic——列表推导 [ i for i in list ]
现在就两种方法进行对比,看看哪种效率高
________________________________________
filter 和 列表推导
file: filter-1.py
1 #coding=utf-8
2 import time
3
4 list = [i for i in range(1,50000)]
5 start = time.time()
6 for i in range(0,1000):
7 list1 = filter(lambda i: i%2==0, list) # filter
8 print time.time() - start
9 #print list1
10

file: filter-2.py
1 #coding=utf-8
2 import time
3
4 list = [i for i in range(1,50000)]
5 start = time.time()
6 for i in range(0,1000):
7 list1 = [i for i in list if i % 2 == 0] # 列表推导
8 print time.time() - start
9 #print list1
10


结果:

\


map和列表推导

1 #File: map-1.py
2 #coding=utf-8
3 import time
4
5 list = [i for i in range(1,50000)]
6 start = time.time()
7 for i in range(0,1000):
8 list1 = map(lambda i: i*2, list)
9 print time.time() - start
10 #print list1
11



#File: map-2.py
#coding=utf-8
import time

list = [i for i in range(1,50000)]
start = time.time()
for i in range(0,1000):
list1 = [ i*2 for i in list ]
print time.time() - start
#print list1


结果:

\


结论
其实两者差别不太大,可以归结为编码风格问题,但是我个人比较喜欢pythonic的列表推导,刚好它的效率也高点!^_^

摘自 hate感冒
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