吴裕雄--天生自然Numpy库学习笔记：NumPy 迭代数组

import numpy as np

a = np.arange(6).reshape(2,3)
print ('原始数组是：')
print (a)
print ('\n')
print ('迭代输出元素：')
for x in np.nditer(a):
    print (x, end=", " )
print ('\n')

import numpy as np

a = np.arange(6).reshape(2,3)
for x in np.nditer(a.T):
    print (x, end=", " )
print ('\n')

for x in np.nditer(a.T.copy(order='C')):
    print (x, end=", " )
print ('\n')

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 ('原始数组的转置是：')
b = a.T
print (b)
print ('\n')
print ('以 C 风格顺序排序：')
c = b.copy(order='C')
print (c)
for x in np.nditer(c):
    print (x, end=", " )
print  ('\n')
print  ('以 F 风格顺序排序：')
c = b.copy(order='F')
print (c)
for x in np.nditer(c):
    print (x, end=", " )

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=", " )

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)

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 ('修改后的数组是：')
for x in np.nditer(a, flags =  ['external_loop'], order =  'F'):
   print (x, end=", " )

如果两个数组是可广播的，nditer 组合对象能够同时迭代它们。 假设数组 a 的维度为 3X4，数组 b 的维度为 1X4 ，则使用以下迭代器（数组 b 被广播到 a 的大小）
import numpy as np 

a = np.arange(0,60,5)
a = a.reshape(3,4)
print  ('第一个数组为：')
print (a)
print  ('\n')
print ('第二个数组为：')
b = np.array([1,  2,  3,  4], dtype =  int)
print (b)
print ('\n')
print ('修改后的数组为：')
for x,y in np.nditer([a,b]):
    print ("%d:%d"  %  (x,y), end=", " )