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  • numpy下的flatten()函数用法

    flatten是numpy.ndarray.flatten的一个函数,其官方文档是这样描述的:

    ndarray.flatten(order='C')

    Return a copy of the array collapsed into one dimension.

    Parameters:

     

    order : {‘C’, ‘F’, ‘A’, ‘K’}, optional

    ‘C’ means to flatten in row-major (C-style) order. ‘F’ means to flatten in column-major (Fortran- style) order. ‘A’ means to flatten in column-major order if a is Fortran contiguous in memory, row-major order otherwise. ‘K’ means to flatten a in the order the elements occur in memory. The default is ‘C’.

    Returns:

    y : ndarray

    A copy of the input array, flattened to one dimension.

      

    即返回一个折叠成一维的数组。但是该函数只能适用于numpy对象,即array或者mat,普通的list列表是不行的。

    例子:

    1、用于array对象

    from numpy import *
    
    >>>a=array([[1,2],[3,4],[5,6]])  ###此时a是一个array对象
    >>>a
    array([[1,2],[3,4],[5,6]])
    
    >>>a.flatten()
    array([1,2,3,4,5,6])
    

     2、用于mat对象

    >>> a=mat([[1,2,3],[4,5,6]])
    >>> a
    matrix([[1, 2, 3],
            [4, 5, 6]])
    >>> a.flatten()
    matrix([[1, 2, 3, 4, 5, 6]])

     3、但是该方法不能用于list对象

    >>> a=[[1,2,3],[4,5,6],['a','b']]
    >>> a
    [[1, 2, 3], [4, 5, 6], ['a', 'b']]
    >>> a.flatten()                      ###报错
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    AttributeError: 'list' object has no attribute 'flatten'
    

     想要list达到同样的效果可以使用列表表达式:

    >>> [y for x in a for y in x]
    [1, 2, 3, 4, 5, 6, 'a', 'b']
    
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  • 原文地址:https://www.cnblogs.com/itdyb/p/5796834.html
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