Search and replace a line in a file in Python

Question

I want to loop over the contents of a text file and do a search and replace on some lines and write the result back to the file. I could first load the whole file in memory

Answer 1

fileinput is quite straightforward as mentioned on previous answers:

import fileinput

def replace_in_file(file_path, search_text, new_text):
    with fileinput.input(file_path, inplace=True) as f:
        for line in f:
            new_line = line.replace(search_text, new_text)
            print(new_line, end='')

Explanation:

• fileinput can accept multiple files, but I prefer to close each single file as soon as it is being processed. So placed single file_path in with statement.
• print statement does not print anything when inplace=True, because STDOUT is being forwarded to the original file.
• end='' in print statement is to eliminate intermediate blank new lines.

Can be used as follows:

file_path = '/path/to/my/file'
replace_in_file(file_path, 'old-text', 'new-text')