#!/usr/bin/env python3

import os
from sys import argv

rows = {}

with open("students.textdb", "rt") as file:
    for line in file.readlines():
        idx, lab, proj, exam = line.strip().split(" ")
        rows[int(idx)] = (idx, lab, proj, exam)

# argv is like
# ["set_student_1.py", "512345", "5.0", "3.0", "3.0"]
rows[int(argv[1])] = tuple(argv[1:5])

with open("students-tmp.textdb", "wt") as file:
    for _, (idx, lab, proj, exam) in sorted(dict.items(rows)):
        print(idx, lab, proj, exam, file=file)
    file.flush() # make sure buffered data got passed to OS kernel
    os.fsync(file.fileno()) # make sure data got written to disk

os.rename("students-tmp.textdb", "students.textdb")