python中星号*用法小结

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1. 用法一：实现zip的逆操作

    he=[[1,2,3,4],[5,6,7,8],[9,10,11,12]]
    >>> [[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]]
    zip(he)
    >>> [([1, 2, 3, 4],), ([5, 6, 7, 8],), ([9, 10, 11, 12],)]
    zip(*he)
    >>> [(1, 5, 9), (2, 6, 10), (3, 7, 11), (4, 8, 12)]
    zip(*zip(he))
    >>> [([1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12])]

2. 用法二：星号表达式-代替多个元素

    >>> cc
    [1, 3, 4, 5, 7]
    >>> a,*b,c
    (1, 3, 4, 5, 7)
    >>> b
    [3, 4, 5]

3. 用法三：数学计算

    def hah(*args,**kwargs):
        for i in args:
            print '{0}的3次幂={1}'.format(i, i ** 3)
            print '{0}乘以3={1}'.format(i, i * 3)
        print '把接收的参数作为元组压缩: ', zip(args)
        print '把接收的参数作为元组解压: ', zip(*zip(args))
        print '把接收的参数作为字典打印: ',kwargs
    hah(2,4,6,pd='pandas',np='numpy',pm='pymongo')
    输出：
    2的3次幂=8
    2乘以3=6
    4的3次幂=64
    4乘以3=12
    6的3次幂=216
    6乘以3=18
    把接收的参数作为元组压缩:  [(2,), (4,), (6,)]
    把接收的参数作为元组解压:  [(2, 4, 6)]
    把接收的参数作为字典打印:  {'np': 'numpy', 'pd': 'pandas', 'pm': 'pymongo'}