Append String to each line of .txt file in python?

Question

I want to append some text to every line in my file

Here is my code

filepath = 'hole.txt'
with open(filepath) as fp:
    line = fp.readline()
    cnt = 1
    while line:
        #..........
        #want to append text "#" in every line by reading line by line 
        text from .txt file
        line = fp.readline()
        cnt += 1

Does it help? https://stackoverflow.com/questions/3277503/in-python-how-do-i-read-a-file-line-by-line-into-a-list?rq=1 — Kefeng91, May 10 '18 at 08:06

Maxime Chéramy · Accepted Answer · 2018-05-10T08:19:41.287

14

You can read the lines and put them in a list. Then you open the same file with write mode and write each line with the string you want to append.

filepath = "hole.txt"
with open(filepath) as fp:
    lines = fp.read().splitlines()
with open(filepath, "w") as fp:
    for line in lines:
        print(line + "#", file=fp)

edited May 10 '18 at 08:19

answered May 10 '18 at 08:10

Maxime Chéramy

17,761
8
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1

Downvoter: please explain so I can improve my answer. – Maxime Chéramy May 10 '18 at 08:14
2

(same struggle here). Happy to learn about that `file=fp` in the `print()` method though. Works. – arnaud May 10 '18 at 08:15
i make it working in my way... reallllllyyyyyyyyyyyyyyyyy great. – Muhammad Hamaad Latif May 10 '18 at 09:38

score 6 · Answer 2 · answered May 10 '18 at 08:11

Assuming you can load the full text in memory, you could open the file, split by row and for each row append the '#'. Then save :-) :

with open(filepath, 'r') as f:     # load file
    lines = f.read().splitlines()  # read lines

with open('new_file.txt', 'w') as f: 
    f.write('\n'.join([line + '#' for line in lines]))  # write lines with '#' appended

score 1 · Answer 3 · answered May 10 '18 at 08:21

I'll assume the file is small enough to keep two copies of it in memory:

filepath = 'hole.txt'
with open(filepath, 'r') as f:
    original_lines = f.readlines()

new_lines = [line.strip() + "#\n" for line in original_lines]

with open(filepath, 'w') as f:
    f.writelines(new_lines)

First, we open the file and read all lines into a list. Then, a new list is generated by strip()ing the line terminators from each line, adding some additional text and a new line terminator after it.

Then, the last line overwrites the file with the new, modified lines.

score 1 · Answer 4 · answered May 10 '18 at 08:29

1

does this help?

inputFile = "path-to-input-file/a.txt"
outputFile = "path-to-output-file/b.txt"
stringToAPpend = "#"

with open(inputFile, 'r') as inFile, open(outputFile, 'w') as outFile:
    for line in inFile:
        outFile.write(stringToAPpend+line)

answered May 10 '18 at 08:29

Ankush Rathi

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1
6
26

thanks its working. :) but what i want that i want to do such kinda thing in a single file which is created before. mean that want to append in the old created file. – Muhammad Hamaad Latif May 10 '18 at 09:08
so you want to replace the original file and not create a new file, right? – Ankush Rathi May 10 '18 at 09:15
yeah have got it. tried your provided snippet and modified it too according to my work. Really thanks for indeed help. :) – Muhammad Hamaad Latif May 10 '18 at 09:58

Append String to each line of .txt file in python?

4 Answers4