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  • Python内置函数(67)——zip

    英文文档:

    zip(*iterables)

    Make an iterator that aggregates elements from each of the iterables.

    Returns an iterator of tuples, where the i-th tuple contains the i-th element from each of the argument sequences or iterables. The iterator stops when the shortest input iterable is exhausted. With a single iterable argument, it returns an iterator of 1-tuples. With no arguments, it returns an empty iterator.

    The left-to-right evaluation order of the iterables is guaranteed. This makes possible an idiom for clustering a data series into n-length groups using zip(*[iter(s)]*n). This repeats the same iterator n times so that each output tuple has the result of n calls to the iterator. This has the effect of dividing the input into n-length chunks.

    说明:

      1. 函数功能是聚合传入的每个迭代器中相同位置的元素,返回一个新的元组类型迭代器。

    >>> x = [1,2,3]
    >>> y = [4,5,6]
    >>> xy = zip(x,y)
    >>> xy #xy的类型是zip类型
    <zip object at 0x0429C828>
    #导入Iterable
    >>> from collections import Iterable
    >>> isinstance(xy,Iterable) #判断是否可迭代对象
    True
    >>> list(xy) #结果
    [(1, 4), (2, 5), (3, 6)]

      2. 如果传入的迭代器长度不一致,最短长度的迭代器迭代结束后停止聚合。

    >>> x = [1,2,3] #长度3
    >>> y = [4,5,6,7,8] #长度5
    >>> list(zip(x,y)) # 取最小长度3
    [(1, 4), (2, 5), (3, 6)]

      3. 如果只传入一个迭代器,则返回的单个元素元组的迭代器。

    >>> list(zip([1,2,3]))
    [(1,), (2,), (3,)]

      4. 如果不传入参数,则返回空的迭代器。

    >>> list(zip())
    []

      5. zip(*[iter(s)]*n)等效于调用zip(iter(s),iter(s),...,iter(s))。

    >>> x = [1,2,3]
    
    >>> list(zip(*[x]*3))
    [(1, 1, 1), (2, 2, 2), (3, 3, 3)]
    
    >>> list(zip(x,x,x))
    [(1, 1, 1), (2, 2, 2), (3, 3, 3)]
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  • 原文地址:https://www.cnblogs.com/sesshoumaru/p/6130095.html
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