Write и append.

Режими на open: - "w" — пише (създава или презаписва) - "a" — добавя в края

with open("log.txt", "w", encoding="utf-8") as f: f.write("start\n") with open("log.txt", "a", encoding="utf-8") as f: f.write("end\n")

with open("log.txt", encoding="utf-8") as f: print(f.read())

write() не добавя автоматично нов ред — добавяш \n сам.