Delete text using file operators in python

Say there is a code:

with open("example.pdf", "r") as file:
  String = file.seek(-11, os.SEEK_END)
  print(String)

and the output is Hello Hello

How would you change the text in the file "example.pdf" so that everything after the first Hello is deleted using file operators(read/write/append)?

Thank you for your help!!

Open the file in the appropriate mode. Determine the offset where you want to truncate the file. Call truncate() and close the file.

For example (for a plain text file):

import os
def remove_after(filename, text):
    with open(filename, 'r+') as f:
        contents = f.read()
        offset = contents.find(text)
        if offset >= 0:
            pos = offset + len(text)
            f.seek(pos, os.SEEK_SET)
            f.truncate()
remove_after('/Volumes/G-Drive/foo.txt', 'hello')

For a binary file the mode should be rb+ and the mechanism for determining the truncation point is likely to be different.

Bear in mind though that deleting arbitrary content from a binary file may break its internal structure depending on what the file is