Python: How do I insert a string into a specific spot in a .txt file?

Question

I have a .txt file with a variable called id=

How can I write a script that will look into that .txt file, find id= and insert a string right after the =?

I do have a separate .py file called dictionary that contains a dictionary with the purpose of finding and replacing certain words in the .txt file.

Could I also use this dictionary as a way to find and insert?

Short answer: You need to read the entire file again, insert the new data when you parse "id=" and then write the file again. — tst, Nov 26 '19 at 14:24
see e.g. [this](https://stackoverflow.com/a/58378296/10197418) — FObersteiner, Nov 26 '19 at 14:31

Fakher Mokadem · Accepted Answer · 2019-11-26T14:42:08.553

Read the file line by line, if line has 'id=' replace it with the builtin replace method of str and write the new line, else write the old line.

with open(path_to_file) as fp:
  with open(path_to_new_file, 'w') as nfp:
    string = "whatever"
      for line in fp: 
        if "id=" in line:
          new_line = line.replace("id=", f"id={string}")
          print(f"replacing {line} with {new_line}")
          nfp.write(new_line)
        else: 
          nfp.write(line)

Python: How do I insert a string into a specific spot in a .txt file?

1 Answers1