How to programmatically edit a text file?

Question

I have a file called "answer" with "NO" written in it. But in a certain moment of my code I want to change it to "YES".

Doing this:

file = open("answer.txt", mode="r", encoding="utf-8")
read = file.read()
print(read)

The output is: NO

I know mode = "a" stands for "to add", but I don't want to add a "YES", I want to erase the NO and write YES.

How do I edit a file, or a line in a file?

You have to close and reopen it with "w" to rewrite the file. — RufusVS, May 08 '22 at 14:49
Minor (pedantic) correction: 'a' is for *append*. 'w' (write mode) first truncates (erases current content) then enables writing. — S3DEV, May 08 '22 at 14:51

score 2 · Answer 1 · answered May 08 '22 at 14:51

2

Use with syntax you don't need to close the file.


with open("answer.txt", mode = "w", encoding = "utf-8") as file:
    file.write("YES")

answered May 08 '22 at 14:51

codester_09

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FLAK-ZOSO · Answer 2 · 2022-05-08T15:02:50.773

mode = "a" stands for "to add", but I don't want to add a "YES", I want to erase the NO and write YES.

You want to erase the previous content of the file? Use 'w' mode!

file = open("answer.txt", mode = "w", encoding = "utf-8")
file.write("YES")
file.close() # Now answer.txt contains only "YES"

To avoid calling that unestetic file.close you can take advantage of _io.TextIOWrapper's method __enter__ using a with/as block:

with open("answer.txt", 'w') as file:
    file.write("YES")

You should know that 'a' doesn't stand for "add" but for "append", and that there are other options that you can find in the documentation here.

How do I edit a file, or a line in a file?

This second question is more complicated, you will have to do the following:

Open the file
Read the file
Split the file in lines (or directly read it using .readlines())
Iterate through lines until you find the one you want to edit
Edit the line
Write to the file

How to programmatically edit a text file?

2 Answers2

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