numpy的阵列整数/浮点除法 [英] Numpy array integer / float division

问题描述

我发现在Python / numpy的以下行为有些奇怪：

I found the following behaviour in Python/numpy somewhat strange:

In [51]: a = np.arange(10, 20)
In [52]: a = a / 10.0
In [53]: a
Out[53]: array([ 1. ,  1.1,  1.2,  1.3,  1.4,  1.5,  1.6,  1.7,  1.8,  1.9])

In [54]: a = np.arange(10, 20)
In [55]: a /= 10.0
In [56]: a
Out[56]: array([1, 1, 1, 1, 1, 1, 1, 1, 1, 1])

我觉得 A = A / 10.0 和 A / = 10.0 应返回相同的结果。难道这inteded某处记录？

I felt that a=a/10.0 and a/=10.0 should return the same result. Is this inteded and documented somewhere?

推荐答案

与 A / = 10.0 是它修改到位数组，并赢得了问题T改变数组的DTYPE，所以所有的花车转换为整数。在另一方面 A = A / 10.0 创建一个新的数组，如果正在创建一个新的数组类型是可以改变的。

The problem with a /= 10.0 is that it modifies the array in place, and it won't change the the dtype of the array, so all the floats are converted to integers. On the other hand a = a / 10.0 created a new array, and the type can be changed if a new array is being created.

从<一个href=\"http://docs.scipy.org/doc/numpy/user/basics.indexing.html#assigning-values-to-indexed-arrays\">docs:

注意分配可能导致的变化，如果指定更高的类型
  降低类型（如浮点数到整数），甚至异常（分配
  复杂浮动或整数）：

Note that assignments may result in changes if assigning higher types to lower types (like floats to ints) or even exceptions (assigning complex to floats or ints):

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