Detailed introduction to the itertools module in Python

高洛峰
Release: 2017-03-20 11:07:04
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itertools module: cycler

1, infinite cycler:count,cycle,repeat

(1)count(5,3) #从5开始的整数循环器,每次增加3,即:5,8,11,14,17...from itertools import *import time a = count(5,3)for i in a: print(i) time.sleep(1) 输出结果为:5 8 11 14 17 20 23 26
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(2)cycle('zxy') #重复元素x y z x y z x y z... from itertools import *import time s = cycle('xyz')for i in s: print(i) time.sleep(1) 输出结果为: x y z x y z x y z
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repeat() #重复元素例1:from itertools import *import time s = repeat(3.14) #无限重复元素for i in s: print(i) time.sleep(1) 输出结果为:3.14 3.14 3.14 3.14 3.14 3.14例2:from itertools import *import time s = repeat(3,5) #重复元素3,共5次for i in s: print(i) time.sleep(1) 输出结果为:3 3 3 3 3
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Two,Function-style tools: starmap, takewhile, dropwhile

(1)starmap() #跟map类似from itertools import *s = starmap(pow,[(1,1),(2,2),(3,3)]) #pow()求指数1**1,2**2,3**3for i in s: print(i) 输出结果为:1 4 27(2)takewhile() #当函数返回True时,收集元素到循环器。一旦函数返回False,则停止。from itertools import *s1 = takewhile(lambda x: x < 5, [1,2,3,4,5,6,7])for i in s1: print(i) 输出结果为:1 2 3 4(3)dropwhile() #与takewhile相反。s2 = dropwhile(lambda x: x < 5, [1,2,3,4,5,6,7])for i in s2: print(i) 输出结果为:5 6 7
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