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1. The Python Library Reference

2. BuiltIn函数

• enumerate
  • 作用：以迭代的方式为序列中的所有元素生成带序号的tuple
  • 调用：enumerate(iterable, 'start='number)
  • 说明：iterable必须是支持迭代的对象，例如list；start=为可选的固定字符；number为数字，如0、1、2等

    # 输出tuple
    >>> seasons = ['Spring', 'Summer', 'Fall', 'Winter']
    >>> print(list(enumerate(seasons)))
    [(0, 'Spring'), (1, 'Summer'), (2, 'Fall'), (3, 'Winter')]
    >>> print(list(enumerate(seasons，start=3)))
    [(3, 'Spring'), (4, 'Summer'), (5, 'Fall'), (6, 'Winter')]
    # 输出序号列表(注意for后的下划线)
    >>> xs = [i + 0.1 for i, _ in enumerate(seasons)]
    >>> print(xs)
    [0.1, 1.1, 2.1, 3.1]
    # 输出值列表(注意for后的下划线)
    >>> ys = [season + '+' for _, season in enumerate(seasons)]
    >>> print(ys)
    ['Spring+', 'Summer+', 'Fall+', 'Winter+']
    

• zip
  • 作用：根据不同迭代对象中相同的索引，以迭代的方式为序列中的所有元素生成tuple
  • 调用：zip(*iterables)
  • 说明：*iterables表示多个支持迭代的对象，所有对象不需要有相同的长度，根据相同索引并按照其中最少的索引生成tuple，如果其中任意1个迭代对象为空，则生产空tuple

    # 迭代对象长度相同
    >>> x = [1, 2, 3]
    >>> y = [4, 5, 6]
    >>> zipped = zip(x, y)
    >>> print(list(zipped))
    [(1, 4), (2, 5), (3, 6)]
    # 迭代对象长度不同
    >>> x = [1, 2, 3]
    >>> y = [4, 5]
    >>> zipped = zip(x, y)
    >>> print(list(zipped))
    [(1, 4), (2, 5)]
    # 迭代对象多于2个
    >>> x = [1, 2, 3]
    >>> y = [4, 5, 6]
    >>> z = [7, 8, 9, 10]
    >>> zipped = zip(x, y, z)
    >>> print(list(zipped))
    [(1, 4, 7), (2, 5, 8), (3, 6, 9)]
    # 迭代对象中有1个为空
    >>> x = [1, 2]
    >>> y = []
    >>> zipped = zip(x, y)
    >>> print(list(zipped))
    []