Writing to a file in Python inserts null bytes
- by Javier Badia
I'm writing a todo list program. It keeps a file with a thing to do per line, and lets the user add or delete items. The problem is that for some reason, I end up with a lot of zero bytes at the start of the file, even though the item is correctly deleted. I'll show you a couple of screenshots to make sure I'm making myself clear.
This is the file in Notepad++ before running the program:
This is the file after deleting item 3 (counting from 1):
This is the relevant code. The actual program is bigger, but running just this part triggers the error.
import os
TODO_FILE = r"E:\javi\code\Python\todo-list\src\todo.txt"
def del_elems(f, delete):
"""Takes an open file and either a number or a list of numbers, and deletes the
lines corresponding to those numbers (counting from 1)."""
if isinstance(delete, int):
delete = [delete]
lines = f.readlines()
f.truncate(0)
counter = 1
for line in lines:
if counter not in delete:
f.write(line)
counter += 1
f = open(TODO_FILE, "r+")
del_elems(f, 3)
f.close()
Could you please point out where's the mistake?
