Use of 'numpy' package in Python

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Import

import numpy or import numpy as np

Feature

The key feature of numpy package is that it introduce a new data structure -- array

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>>>import numpy as np
>>>a = np.array([1,2,3])
a
array([1, 2, 3])
>>>type(a)
<class 'numpy.ndarray'>

Propertities of array

ndarray 的重要属性包括:

  1. ndarray.ndim：数组的维数，也称为rank
  2. ndarray.shape：数组各维的大小，对一个n行m列的矩阵来说， shape 为 (n,m)
  3. ndarray.size：元素的总数。
  4. ndarray.dtype：每个元素的类型，可以是numpy.int32, numpy.int16, and numpy.float64等
  5. ndarray.itemsize：每个元素占用的字节数。
  6. ndarray.data：指向数据内存。

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