**numpy.savetxt(fname,array,fmt='%.18e',delimiter=None,newline='\n', header='', footer='', comments='# ', encoding=None)**

import numpy as np
arr = np.arange(12).reshape(3,4)
#fmt缺省取%.18e(浮點(diǎn)數(shù)）
#分割符默認(rèn)是空格，寫入文件保存在當(dāng)前目錄
np.savetxt('test-1.txt',arr)
#fmt:%d 寫入文件的元素是十進(jìn)制整數(shù),分割符為逗號",",寫入文件保存在當(dāng)前目錄
np.savetxt('test-2.txt',arr,fmt='%d',delimiter=',')
#在test-3.txt文件頭部和尾部增加注釋，頭部 #test-3，尾部 # 數(shù)據(jù)寫入注釋，寫入文件的元素是字符串
np.savetxt('test-3.txt',arr,fmt='%s',delimiter=',',header=\
  'test-3',footer='測試數(shù)據(jù)',encoding='utf-8')
#在test-4.txt文件頭部加##test-4注釋
np.savetxt('test-4.txt',arr,fmt='%f',delimiter=',',header=
  'test-4',comments='###')
#將arr數(shù)組保存為csv文件
np.savetxt('test-1.csv',arr,fmt='%d',header='test-1')

a = np.loadtxt('test-1.txt') 
#讀入當(dāng)前目錄下的文件 test-1.txt
print(a) 
[[ 0. 1. 2. 3.]
 [ 4. 5. 6. 7.]
 [ 8. 9. 10. 11.]]

# skiprows:指跳過前1行, 如果設(shè)置skiprows=2, 就會(huì)跳過前兩行,數(shù)據(jù)類型設(shè)置為整型.
a = np.loadtxt('test-1.txt', skiprows=1, dtype=int)
print(a)
[[ 4 5 6 7]
 [ 8 9 10 11]]

# comment, 如果行的開頭為#就會(huì)跳過該行
a = np.loadtxt('test-4.txt', skiprows=2, comments='#',delimiter=',')
b = np.loadtxt('test-4.txt',comments='#',delimiter=',')
print(a,b,sep='\n')
[[ 4. 5. 6. 7.]
 [ 8. 9. 10. 11.]]
[[ 0. 1. 2. 3.]
 [ 4. 5. 6. 7.]
 [ 8. 9. 10. 11.]]

# usecols:指定讀取的列，若讀取0,2兩列
aa = np.loadtxt('test-3.txt',dtype=int, skiprows=1,delimiter=',',usecols=(0, 2))
#unpack是指會(huì)把每一列當(dāng)成一個(gè)向量輸出, 而不是合并在一起。
(a, b) = np.loadtxt('test-2.txt', dtype=int, skiprows=1,
   comments='#', delimiter=',',
   usecols=(0, 2), unpack=True)
print(aa,a, b,sep='\n')
[[ 0 2]
 [ 4 6]
 [ 8 10]]
[4 8]
[ 6 10]
#讀取csv文件
aa = np.loadtxt('test-1.csv',skiprows=1)
print(aa)
[[ 0. 1. 2. 3.]
 [ 4. 5. 6. 7.]
 [ 8. 9. 10. 11.]]

numpy.save(file,array)
numpy.savez(file,array)

import numpy as np
a = np.arange(12).reshape(3,4)
print('原數(shù)組a:\n',a)
np.save('arr1.npy', a) #將數(shù)據(jù)存儲(chǔ)為npy,保存時(shí)可以省略擴(kuò)展名，默認(rèn).npy
c = np.load('arr1.npy') #讀取arr1.npy的數(shù)據(jù),讀取數(shù)據(jù)時(shí)不能省略 .npy
print('讀取后的數(shù)據(jù)：\n',c)

ar = np.arange(6).reshape(3,2) 

print('保存前的數(shù)組:',a,ar,sep='\n')
np.savez('arr2.npz',a,ar) #多數(shù)組存儲(chǔ)，默認(rèn)文件名.npz
b = np.load('arr2.npz')
print('讀取后的數(shù)據(jù)：')
print(b['arr_0'],b['arr_1'],sep='\n')

for i in b.items():
 print(i)
('a', array([[ 0, 1, 2, 3],
 [ 4, 5, 6, 7],
 [ 8, 9, 10, 11]]))
('ar', array([[0, 1],
 [2, 3],
 [4, 5]]))