python,itertools模块

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    itertools模块的使用:

# coding=utf-8

"""
itertools模块
"""

import itertools
import unittest

class TestItertools(unittest.TestCase):

    def test_count(self):
        """itertools.count()无限产生自然数"""
        natuals = itertools.count(1, 1)
        res = 0
        for r in natuals:
            if r == 10:
                res = r
                break
        self.assertEqual(10, res)

    def test_cycle(self):
        """itertools.cycle()无限重复序列里面的值"""
        my_list = "ABC"
        result = []
        for num, res in enumerate(itertools.cycle(my_list)):
            result.append(res)
            if num == 5:
                break
        self.assertEqual([A,B,C,A,B,C], result)

    def test_repeat(self):
        """itertools.repeat(‘A‘,3) 重复A 3次"""
        result = [res for res in itertools.repeat(ABC, 3)]
        self.assertEqual([ABC, ABC, ABC], result)

    def test_takewhile(self):
        """itertools.takewhile()截取一个有限的序列"""
        natuals = itertools.count(0)
        result = itertools.takewhile(lambda x : x <= 5, natuals)
        self.assertEqual([0, 1, 2, 3, 4, 5], list(result))

    def test_chain(self):
        """itertools.chain()将两个迭代对象组成一个迭代对象"""
        iter1 = [A,B]
        iter2 = CCC
        result = itertools.chain(iter1, iter2)
        self.assertEqual([A, B, C, C, C], list(result))

    def test_groupby(self):
        """groupby()把迭代器中相邻的重复元素挑出来放在一起"""
        text = "AAAAAACCCCDDDDMMM"
        result = {key : list(val) for key, val in itertools.groupby(text)}
        self.assertEqual([M, M, M], result[M])

if __name__ == __main__:
    unittest.main()

 

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