numpy学习(一)

（一）基础学习

学习渠道：阿里天池AI学习——Numpy基础（传送门）

（二）练习篇

练习渠道：Numpy基础100题（Part 1）

1. Import the numpy package under the name np(★☆☆)


 import numpy as np 

2. Print the numpy version and the configuration(★☆☆)

 print(np.version)
 np.show_config()

3. Create a null vector of size 10(★☆☆)

 arr = np.zeros(10)
 print(arr)

运行结果：[0. 0. 0. 0. 0. 0. 0. 0. 0. 0.]

4. How to find the memory size of any array (★☆☆)

 print("%d bytes" %(arr.size*arr.itemsize))

运行结果：80 bytes

5. How to get the documentation of the numpy add function from the command line? (★☆☆)

np.add?

6. Create a null vector of size 10 but the fifth value which is 1 (★☆☆)

 arr = np.zeros(10)
 arr[4] = 1;
 print(arr)

运行结果：[0. 0. 0. 0. 1. 0. 0. 0. 0. 0.]

7. Create a vector with values ranging from 10 to 49 (★☆☆)

 arr = np.arange(10,50)
 print(arr)

运行结果：[10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49]

8. Reverse a vector (first element becomes last) (★☆☆)

 arr = np.arange(10,50)
 print(arr[::-1])

运行结果：[49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10]

9. Create a 3x3 matrix with values ranging from 0 to 8 (★☆☆)

 arr = np.arange(9).reshape(3,3)
 print(arr)

运行结果：[[0 1 2] [3 4 5] [6 7 8]]

10. Find indices of non-zero elements from [1,2,0,0,4,0] (★☆☆)

 arr = np.array([1,2,0,0,4,0])
 print(arr.nonzero()[0])

运行结果：[0 1 4]