Here is how you can read and write to the same file, removing lines matching "Hello World" from the file. This basically overwrites the entire file but simply does not include the lines containing "Hello World".

#!/usr/bin/python3
with open("/path/to/example.txt", "r+") as file:
  file.readlines = file.read().splitlines()
  file.seek(0)
  for line in file.readlines:
    print(line)
    if line != "Hello World":
      file.write(f"{line}\n")
  file.truncate()