itertools内置库

Posted 2020-10-05 fuzzier

1 itertools.chain(*iterable)

将多个序列作为一个单独的序列返回

import itertools

for ele in itertools.chain(‘We‘, ‘ are ‘, ‘ champion.‘):
    print ele

output:
W
e
 
a
r
e
 
 
c
h
a
m
p
i
o
n
.

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在iter中添加判断类

2 itertools.compress(data, selector)

返回selector为True的data对应元素

import itertools

for ele in itertools.compress(‘qwer‘, [1,0,1,1]):
    print ele

output:
q
e
r

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3 itertools.ifiter(predicate, iterable)

返回predicate结果为True的元素迭代器，如果predicate为None,则返回所有iterable中为True的项

import itertools

for ele in itertools.ifilter(lambda x: x > 5, range(8)):
    print ele

ouput:
6
7

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4 itertools.ifterfalse(predicate, iterable)

与itertools.ifiter()正好相反

 

5 itertools.takewhile(predicate, iterable)

如果predicate为真，则返回iterable元素，如果为假则不再返回，break.

import itertools

for ele in itertools.takewhile(lambda x: x < 5, range(8)):
    print ele

ouput:
0
1
2
3
4

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分类

6 itertools.groupby(iterable[,key])

返回一组（key,itera）,key为iterable的值，itera为等于key的所有项

注意：iterable需要先进行sort

import itertools

for key, ele in itertools.groupby([‘abc‘, ‘awe‘, ‘bjf‘, ‘caf‘, ‘bjf‘], key=lambda x: x[0]):
    print key, tuple(ele)

output:
a (‘abc‘, ‘awe‘)
b (‘bjf‘,)
c (‘caf‘,)
b (‘bjf‘,)

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list变为iterable

7 itertools.imap(function,*iterables)

相当于迭代器方式的map()

8 itertools.islice(iterable, start,stop[,step])

相当于迭代器方式的切片操作

 

无限递增

8 itertools.count(start=0,step=1)

返回以start开始，step递增的序列，无限递增

import itertools
for each in itertools.count(start=0, step=2):
    print each

output:
1
2
3
.
.

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9 itertools.cycle(iterable)

将迭代器进行无限迭代

import itertools
for each in itertools.cycle(‘ab‘):
    print each

output:
a
b
a
b
.

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