标签：10 12 array2 array1 基本操作 array numpy Out
1.3.1 索引¶
1.3.2 切片¶
- 切片
- 跨步
- 索引数组: 针对多为数组的索引
- 索引结合切片
In [1]:
import numpy as np
In [2]:
# 一维数组索引
array1 = np.array([1,2,3,4,5])
array1
Out[2]:
array([1, 2, 3, 4, 5])
In [3]:
# 取第4个数值
array1[3]
Out[3]:
4
In [5]:
array1[-2] # 倒数第2个数字
Out[5]:
4
In [6]:
# 二维数组
array2 = np.arange(14).reshape(2,7)
array2
Out[6]:
array([[ 0, 1, 2, 3, 4, 5, 6],
[ 7, 8, 9, 10, 11, 12, 13]])
In [7]:
# 第一行第三列数字
array2[0,3]
Out[7]:
3
In [8]:
array2[0][3]
Out[8]:
3
In [9]:
array2[-1,-1]
Out[9]:
13
In [10]:
array2[0,-1]
Out[10]:
6
In [11]:
# 三维数组
array3 = np.arange(30).reshape(2,3,5)
array3
Out[11]:
array([[[ 0, 1, 2, 3, 4],
[ 5, 6, 7, 8, 9],
[10, 11, 12, 13, 14]],
[[15, 16, 17, 18, 19],
[20, 21, 22, 23, 24],
[25, 26, 27, 28, 29]]])
In [12]:
array3[0,1,2]
Out[12]:
7
In [13]:
# 切片
array1
Out[13]:
array([1, 2, 3, 4, 5])
In [15]:
array1[0:3] # a~b,a<=x<b
Out[15]:
array([1, 2, 3])
In [16]:
array1[2:6]
Out[16]:
array([3, 4, 5])
In [17]:
array1[2:]
Out[17]:
array([3, 4, 5])
In [20]:
array1[:-1]
Out[20]:
array([1, 2, 3, 4])
In [21]:
# 二维数组的切片
array2
Out[21]:
array([[ 0, 1, 2, 3, 4, 5, 6],
[ 7, 8, 9, 10, 11, 12, 13]])
In [36]:
array2[0:1,:] # 行参数、列参数
Out[36]:
array([[0, 1, 2, 3, 4, 5, 6]])
In [26]:
array2[1:,:] # 行参数、列参数
Out[26]:
array([[ 7, 8, 9, 10, 11, 12, 13]])
In [28]:
array2[:,3:4]
Out[28]:
array([[ 3],
[10]])
In [29]:
array2[0:,3:4]
Out[29]:
array([[ 3],
[10]])
In [30]:
array2[1:,3:4]
Out[30]:
array([[10]])
In [35]:
array2[0:1,3:4]
Out[35]:
array([[3]])
In [32]:
# 三维数组
array3
Out[32]:
array([[[ 0, 1, 2, 3, 4],
[ 5, 6, 7, 8, 9],
[10, 11, 12, 13, 14]],
[[15, 16, 17, 18, 19],
[20, 21, 22, 23, 24],
[25, 26, 27, 28, 29]]])
In [33]:
array3[0:1,2:,:]
Out[33]:
array([[[10, 11, 12, 13, 14]]])
In [34]:
array3[0:1,2:,:][0,0,2]
Out[34]:
12
In [37]:
# 索引多个数值
array1
Out[37]:
array([1, 2, 3, 4, 5])
In [38]:
array1[np.array([0,2,4])] # 获取第1位，第3位，第5位的数值
Out[38]:
array([1, 3, 5])
In [39]:
# 二维数组
array2
Out[39]:
array([[ 0, 1, 2, 3, 4, 5, 6],
[ 7, 8, 9, 10, 11, 12, 13]])
In [40]:
array2[np.array([0,1]),np.array([1,2])] # 获取第1行第2列，第2行第3列数字
Out[40]:
array([1, 9])
In [ ]:
标签：10,
12,
array2,
array1,
基本操作,
array,
numpy,
Out
From： https://www.cnblogs.com/mlzxdzl/p/17767808.html