pythow写入txt文件，我的字符串被数组覆盖

Question

For example

import numpy as np

with open('new2.txt','w') as f:
    f.write('vel.1d\n')
    f.write('base.mod\n')

a1=np.empty(5)
a1.fill(2900)   

np.savetxt('new2.txt',a1,fmt='%4.1f')

But this is my new2.txt

2900.0
2900.0
2900.0
2900.0
2900.0

I need first to write strings,then do some calculations and write down the array.How to do this?

Answer 1

Try this:

h = 'vel.1d\n' + 'base.mod\n' # prepare file header

np.savetxt('new2.txt', a1, fmt = '%4.1f', header = h) # use header

Answer 2

If you use with open('new2.txt','w') as f: , the file is closed after you leave the with block, so savetxt overwrites from the beginning. You could do:

In [1]: import numpy as np

In [2]: a1=np.empty(5)

In [3]: a1.fill(2900)

In [4]: with open('new2.txt', 'w') as f:
    f.write('vel.1d\n')
    f.write('base.mod\n')
    np.savetxt(f,a1,fmt='%4.1f')