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当越界索引在np数组中时,为什么python numpy.delete不会引发indexError

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使用np.delete时,如果使用越界索引,则会引发indexError . 当一个越界索引在np.array中使用并且该数组用作np.delete中的参数时,为什么这不会引发indexError?

np.delete(np.array([0, 2, 4, 5, 6, 7, 8, 9]), 9)

这给出了索引错误,因为它应该(索引9超出范围)

np.delete(np.arange(0,5), np.array([9]))

np.delete(np.arange(0,5), (9,))

给:

array([0, 1, 2, 3, 4])

1 回答

  • 6

    这是一个已知的“功能”,将在以后的版本中弃用 .

    From the source of numpy

    # Test if there are out of bound indices, this is deprecated
    inside_bounds = (obj < N) & (obj >= -N)
    if not inside_bounds.all():
        # 2013-09-24, 1.9
        warnings.warn(
            "in the future out of bounds indices will raise an error "
            "instead of being ignored by `numpy.delete`.",
            DeprecationWarning)
        obj = obj[inside_bounds]
    

    在python中启用DeprecationWarning实际上会显示此警告 . Ref

    In [1]: import warnings
    
    In [2]: warnings.simplefilter('always', DeprecationWarning)
    
    In [3]: warnings.warn('test', DeprecationWarning)
    C:\Users\u31492\AppData\Local\Continuum\Anaconda\Scripts\ipython-script.py:1: De
    precationWarning: test
      if __name__ == '__main__':
    
    In [4]: import numpy as np
    
    In [5]: np.delete(np.arange(0,5), np.array([9]))
    C:\Users\u31492\AppData\Local\Continuum\Anaconda\lib\site-packages\numpy\lib\fun
    ction_base.py:3869: DeprecationWarning: in the future out of bounds indices will
     raise an error instead of being ignored by `numpy.delete`.
      DeprecationWarning)
    Out[5]: array([0, 1, 2, 3, 4])
    

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