Python 数组操作

遍历

import numpy as np 
 
a = np.arange(0,60,5) 
a = a.reshape(3,4)  
print ('原始数组是：')
print (a)
print ('\n')
print ('以 C 风格顺序排序：')
for x in np.nditer(a, order =  'C'):  
    print (x, end=", " )
print ('\n')
print ('以 F 风格顺序排序：')
for x in np.nditer(a, order =  'F'):  
    print (x, end=", " )

遍历时修改

import numpy as np
 
a = np.arange(0,60,5) 
a = a.reshape(3,4)  
print ('原始数组是：')
print (a)
print ('\n')
for x in np.nditer(a, op_flags=['readwrite']): 
    x[...]=2*x 
print ('修改后的数组是：')
print (a)

数组转置

import numpy as np
 
a = np.arange(12).reshape(3,4)
 
print ('原数组：')
print (a )
print ('\n')
 
print ('对换数组：')
print (a.T)

数组连接

import numpy as np

a = np.arange(16).reshape(4, 4)
print(a)
b = np.arange(8).reshape((4, 2))
print(b)
print("--------")
print(np.append(a, b.T, axis=0))
print("--------")
print(np.append(a, b, axis=1))

数组分割

import numpy as np

a = np.arange(16).reshape(4, 4)
print('第一个数组：')
print(a)
print('\n')
print('默认分割（0轴）：')
b = np.split(a,2)
print(b)
print('\n')

print('沿垂直方向分割：')
c = np.split(a,2,1)
print(c)
print('\n')

数组插入元素

import numpy as np
 
a = np.array([[1,2],[3,4],[5,6]])
 
print ('第一个数组：')
print (a)
print ('\n')
 
print ('未传递 Axis 参数。 在插入之前输入数组会被展开。')
print (np.insert(a,3,[11,12]))
print ('\n')
print ('传递了 Axis 参数。 会广播值数组来配输入数组。')
 
print ('沿轴 0 广播：')
print (np.insert(a,1,[11],axis = 0))
print ('\n')
 
print ('沿轴 1 广播：')
print (np.insert(a,1,11,axis = 1))

数组去重

import numpy as np

a = np.random.randint(1, 12, 30)
print(a)
a = np.unique(a)
print(a)

数组排序

import numpy as np

a = np.array([[3, 7], [9, 1]])
print('我们的数组是：')
print(a)
print('\n')
print('调用 sort() 函数：')
print(np.sort(a))
print('\n')
print('按列排序：')
print(np.sort(a, axis=0))
print('\n')
# 在 sort 函数中排序字段
dt = np.dtype([('name', 'S10'), ('age', int)])
a = np.array([("raju", 21), ("anil", 25), ("ravi", 17), ("amar", 27)], dtype=dt)
print('我们的数组是：')
print(a)
print('\n')
print('按 name 排序：')
print(np.sort(a, order='name'))