How to write multiple line in a .txt with Python?

Question

I tried this:

for a in range(5):
    path_error_folder = r'C:\Users\Thomas\Desktop\test'
    if a==3:
        with open(path_error_folder +'/error_report.txt', 'w') as f:
            f.write('a\n')
    else:
        with open(path_error_folder +'/error_report.txt', 'w') as f:
            f.write('b\n')

What I expected:

What I get:

Does somebody have an idea why?

I think what you are looking for; is using `"a"` (append flag) instead of `"w"`, using the write flag just overwrites the file every time you write something to it' — BoredRyuzaki, Jan 20 '22 at 18:44
Does this answer your question? [Difference between modes a, a+, w, w+, and r+ in built-in open function?](https://stackoverflow.com/questions/1466000/difference-between-modes-a-a-w-w-and-r-in-built-in-open-function) — Tomerikoo, Jan 20 '22 at 18:51

score 3 · Answer 1 · answered Jan 20 '22 at 18:46

3

Change your strategy:

path_error_folder = r'C:\Users\Thomas\Desktop\test'
with open(path_error_folder +'/error_report.txt', 'w') as f:
    for a in range(5):
        if a==3:
            f.write('a\n')
        else:
            f.write('b\n')

answered Jan 20 '22 at 18:46

Corralien

109,409
8
28
52

Roberto Caboni · Accepted Answer · 2022-01-21T12:57:23.557

Opening the file with 'w' flag you are writing always at the beginning of the file, so after the first write you basically overwrite it each time.

The only character you see is simply the last one you write.

In order to fix it you have two options: either open the file in append mode ('a'), if you need to preserve your original code structure

for a in range(5):
    path_error_folder = r'C:\Users\Thomas\Desktop\test'
    if a==3:
        with open(path_error_folder +'/error_report.txt', 'a') as f:
            f.write('a\n')
    else:
        with open(path_error_folder +'/error_report.txt', 'a') as f:
            f.write('b\n')

or, definitely better in order to optimize the process, open the file only once

path_error_folder = r'C:\Users\Thomas\Desktop\test'
with open(path_error_folder +'/error_report.txt', 'w') as f:
    for a in range(5):
        if a==3:
            f.write('a\n')
        else:
            f.write('b\n')

score 0 · Answer 3 · answered Jan 20 '22 at 18:46

0

You need to append the file with open(path_error_folder +'/error_report.txt', 'a').

answered Jan 20 '22 at 18:46

kpie

9,588
5
28
50

Appending is bad because is it will not empty the file when the program is ran again. [This answer](https://stackoverflow.com/a/70791797/16001580) is better. – BCT Jan 20 '22 at 18:48
@BCT Who's to say that's wrong? It might actually be required sometimes... – Tomerikoo Jan 20 '22 at 18:58

How to write multiple line in a .txt with Python?

3 Answers3