Project – Student Management System :

import json
import os
from datetime import datetime

# Represents a single student
class Student:
    def __init__(self, student_id, name):
        self.id = student_id
        self.name = name
        self.grades = {}  # subject -> list of grades
        self.attendance = {}  # date (str) -> "Present" or "Absent"

    def add_grade(self, subject, grade):
        self.grades.setdefault(subject, []).append(grade)

    def mark_attendance(self, date_str, status):
        self.attendance[date_str] = status

    def average_grade(self, subject=None):
        if subject:
            grades = self.grades.get(subject, [])
            return sum(grades) / len(grades) if grades else 0.0
        else:
            total, count = 0, 0
            for grades in self.grades.values():
                total += sum(grades)
                count += len(grades)
            return total / count if count else 0.0

    def attendance_summary(self):
        total = len(self.attendance)
        present = list(self.attendance.values()).count("Present")
        return {"Total Days": total, "Present": present, "Absent": total - present}

    def to_dict(self):
        return {
            "id": self.id,
            "name": self.name,
            "grades": self.grades,
            "attendance": self.attendance
        }

    @staticmethod
    def from_dict(data):
        s = Student(data['id'], data['name'])
        s.grades = data.get("grades", {})
        s.attendance = data.get("attendance", {})
        return s


# Manages a list of students
class StudentManager:
    def __init__(self, filename="students.json"):
        self.filename = filename
        self.students = {}
        self.load()

    def add_student(self, student_id, name):
        if student_id in self.students:
            print("❌ Student ID already exists.")
            return
        self.students[student_id] = Student(student_id, name)
        self.save()

    def remove_student(self, student_id):
        if student_id in self.students:
            del self.students[student_id]
            self.save()
            print("✅ Student removed.")
        else:
            print("❌ Student not found.")

    def get_student(self, student_id):
        return self.students.get(student_id)

    def record_grade(self, student_id, subject, grade):
        student = self.get_student(student_id)
        if student:
            student.add_grade(subject, grade)
            self.save()
        else:
            print("❌ Student not found.")

    def record_attendance(self, student_id, date_str, status):
        student = self.get_student(student_id)
        if student:
            student.mark_attendance(date_str, status)
            self.save()
        else:
            print("❌ Student not found.")

    def list_students(self):
        print("\n📋 Students:")
        for s in self.students.values():
            print(f"{s.id} - {s.name}")

    def save(self):
        with open(self.filename, 'w') as f:
            json.dump({sid: s.to_dict() for sid, s in self.students.items()}, f)

    def load(self):
        if not os.path.exists(self.filename):
            return
        with open(self.filename, 'r') as f:
            data = json.load(f)
            self.students = {sid: Student.from_dict(sdata) for sid, sdata in data.items()}


# Command Line Interface
def main():
    manager = StudentManager()

    while True:
        print("\n=== Student Management System ===")
        print("1. Add Student")
        print("2. Remove Student")
        print("3. Record Grade")
        print("4. Record Attendance")
        print("5. Show Grade Report")
        print("6. Show Attendance Summary")
        print("7. List Students")
        print("8. Exit")

        choice = input("Choose an option: ")

        if choice == "1":
            sid = input("Student ID: ")
            name = input("Name: ")
            manager.add_student(sid, name)

        elif choice == "2":
            sid = input("Student ID to remove: ")
            manager.remove_student(sid)

        elif choice == "3":
            sid = input("Student ID: ")
            subject = input("Subject: ")
            try:
                grade = float(input("Grade: "))
                manager.record_grade(sid, subject, grade)
            except ValueError:
                print("⚠️ Invalid grade.")

        elif choice == "4":
            sid = input("Student ID: ")
            date = datetime.now().strftime("%Y-%m-%d")
            status = input("Attendance (Present/Absent): ")
            if status not in ["Present", "Absent"]:
                print("⚠️ Must be 'Present' or 'Absent'.")
                continue
            manager.record_attendance(sid, date, status)

        elif choice == "5":
            sid = input("Student ID: ")
            student = manager.get_student(sid)
            if student:
                print(f"\n📘 Grade Report for {student.name}")
                for subject, grades in student.grades.items():
                    print(f"{subject}: {grades} (avg: {student.average_grade(subject):.2f})")
                print(f"Overall average: {student.average_grade():.2f}")
            else:
                print("❌ Student not found.")

        elif choice == "6":
            sid = input("Student ID: ")
            student = manager.get_student(sid)
            if student:
                summary = student.attendance_summary()
                print(f"\n🗓️ Attendance for {student.name}")
                print(f"Total Days: {summary['Total Days']}")
                print(f"Present: {summary['Present']}")
                print(f"Absent: {summary['Absent']}")
            else:
                print("❌ Student not found.")

        elif choice == "7":
            manager.list_students()

        elif choice == "8":
            print("👋 Goodbye.")
            break

        else:
            print("❌ Invalid option.")


if __name__ == "__main__":
    main()