Question

Clarification:
So if my file has 10 lines:
THe first line is a heading, so I want to append some text at the end of first line

THen I have a list which contains 9 elements..

I want to read that list and append the end of each line with corresponding element..

So basically list[0] to second line, list[1] to third line and so on..

---

I have a file which is delimted by comma.
something like this:

A,B,C
0.123,222,942
......

Now I want to do something like this:

A,B,C,D #append "D" just once
0.123,222,942,99293
............   

This “D” is actually saved in a list so yeah I have this “D”
How do I do this? I mean I know the naive way.
like go thru each line and do something like

string += str(list[i])

Basically how do i append something at the end of the file in pythonic way 🙂

Answer 1

Just create a new file:

data = ['header', 1, 2, 3, 4]

with open("infile", 'r') as inf, open("infile.2", 'w') as outf:
    outf.writelines('%s,%s\n' % (s.strip(), n) for s, n in zip(inf, data))

If you want to “update” the input file, just rename the new one afterwards

import os
os.unlink("infile")
os.rename("infile.2", "infile")