Python: numpy.fliplr()

np.fliplr()的作用

fliplr()是Numpy库中的函数,作用是将数组在左右方向上翻转.
需要注意的是,fliplr()在左右方向上翻转每行的元素,列保持不变,但是列的显示顺序变了.
下面我们来看一下github上给出的fliplr()函数的source代码:

def fliplr(m):
    """
    Flip array in the left/right direction.
    Flip the entries in each row in the left/right direction.
    Columns are preserved, but appear in a different order than before.
    Parameters
    ----------
    m : array_like
        Input array, must be at least 2-D.
    Returns
    -------
    f : ndarray
        A view of `m` with the columns reversed.  Since a view
        is returned, this operation is :math:`\\mathcal O(1)`.
    See Also
    --------
    flipud : Flip array in the up/down direction.
    rot90 : Rotate array counterclockwise.
    Notes
    -----
    Equivalent to m[:,::-1]. Requires the array to be at least 2-D.

    >>> A = np.diag([1.,2.,3.])
    >>> A
    array([[ 1.,  0.,  0.],
           [ 0.,  2.,  0.],
           [ 0.,  0.,  3.]])
    >>> np.fliplr(A)
    array([[ 0.,  0.,  1.],
           [ 0.,  2.,  0.],
           [ 3.,  0.,  0.]])
    >>> A = np.random.randn(2,3,5)
    >>> np.all(np.fliplr(A) == A[:,::-1,...])
    True
    """
    m = asanyarray(m)
    if m.ndim < 2:
        raise ValueError("Input must be >= 2-d.")
    return m[:, ::-1]

再来举一个例子:

import numpy as np
  
array = np.arange(8).reshape((2,2,2)) 
print("Original array : \n", array) 
  
# fliplr : means flip left-right 
print("\nFlipped array left-right : \n", np.fliplr(array)) 

输出结果为:

Original array : 
 [[[0 1]
  [2 3]]

 [[4 5]
  [6 7]]]

Flipped array left-right : 
 [[[2 3]
  [0 1]]

 [[6 7]
  [4 5]]]

参考资料
[1] numpy.fliplr()
[2] https://www.geeksforgeeks.org/numpy-fliplr-python/

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