首先导入numpy
In [1]:mport numpy as np
In [2]:t = np.arange(80).reshape(20,4)
In [3]: t
Out[3]:
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, 30, 31],
[32, 33, 34, 35],
[36, 37, 38, 39],
[40, 41, 42, 43],
[44, 45, 46, 47],
[48, 49, 50, 51],
[52, 53, 54, 55],
[56, 57, 58, 59],
[60, 61, 62, 63],
[64, 65, 66, 67],
[68, 69, 70, 71],
[72, 73, 74, 75],
[76, 77, 78, 79]])
- 1、行操作
-- 1）取单行
In [4]:t[2] # 取第二行
Out[4]: array([ 8, 9, 10, 11])
-- 2）取多行—取连续多行
In [5]:t[2:]
array([[ 8, 9, 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, 50, 51],
[52, 53, 54, 55],
[56, 57, 58, 59],
[60, 61, 62, 63],
[64, 65, 66, 67],
[68, 69, 70, 71],
[72, 73, 74, 75],
[76, 77, 78, 79]])
-- 3）取多行—取不连续多行
In [6]:t[[2,5,8,12,16]] # 取不连续多行，一定是方括号套方括号才符合语法规则
Out[6]:
array([[ 8, 9, 10, 11],
[20, 21, 22, 23],
[32, 33, 34, 35],
[48, 49, 50, 51],
[64, 65, 66, 67]])
- 2、列操作 ☆☆☆☆☆☆延伸操作
In [7]:t[:2,:] #ｔ［，］，＂，＂前是行操作，＂，＂之后是列操作
Out[7]:
array([[0, 1, 2, 3], # 取前3行 和所有列
[4, 5, 6, 7]])
In [8]: t[[2,5,8,12,16],:] # 取2、5、8、12、16行，以及取全部列数据
Out[8]:
array([[ 8, 9, 10, 11], # 请比较以上多行操作
[20, 21, 22, 23],
[32, 33, 34, 35],
[48, 49, 50, 51],
[64, 65, 66, 67]])
In [11]:t[:,２] # 取一列（第３列）数据
Out[11]: array([ 2, 6, 10, 14, 18, 22, 26, 30, 34, 38, 42, 46, 50, 54, 58, 62, 66,
70, 74, 78])
In [1２]:t[:,:2] # 取连续多列
Out[1２]:
array([[ 0, 1],
[ 4, 5],
[ 8, 9],
[12, 13],
[16, 17],
[20, 21],
[24, 25],
[28, 29],
[32, 33],
[36, 37],
[40, 41],
[44, 45],
[48, 49],
[52, 53],
[56, 57],
[60, 61],
[64, 65],
[68, 69],
[72, 73],
[76, 77]])
In [13]:t[:,[0,2]] # 取不连续多列（第0列和第2列）
Out[13]:
array([[ 0, 2],
[ 4, 6],
[ 8, 10],
[12, 14],
[16, 18],
[20, 22],
[24, 26],
[28, 30],
[32, 34],
[36, 38],
[40, 42],
[44, 46],
[48, 50],
[52, 54],
[56, 58],
[60, 62],
[64, 66],
[68, 70],
[72, 74],
[76, 78]])
- 3 、行和列操作
In [21]:t[6,2] # 1 取6行2列
Out[21]: 26
In [22]:t[3:6,1:3] # 2 取第4行到第6行，第2列到3列
Out[22]:
array([[13, 14],
[17, 18],
[21, 22]])
In [30]:t[[3,6,13],[0,2,3]]# 3 这种取值方式，只能取到某个或某些点，列和行数要对应，否则要报错☆☆☆☆☆☆
Out[30]: array([12, 26, 55])