Final Project: Build a Student Grade Calculator

class Student:
    """Represents a single student with grades."""
    
    def __init__(self, name, student_id):
        self.name = name
        self.student_id = student_id
        self.grades = {}      # {subject: score}
    
    def add_grade(self, subject, score):
        """Add or update a grade for a subject."""
        if not (0 <= score <= 100):
            print(f"  ✗ Score must be between 0 and 100 (got {score})")
            return False
        self.grades[subject] = score
        print(f"  ✓ Added: {subject} = {score}")
        return True
    
    def get_average(self):
        """Calculate the average score across all subjects."""
        if not self.grades:
            return 0.0
        return sum(self.grades.values()) / len(self.grades)
    
    def get_letter_grade(self):
        """Convert numerical average to a letter grade."""
        avg = self.get_average()
        if avg >= 90:   return 'A'
        elif avg >= 80: return 'B'
        elif avg >= 70: return 'C'
        elif avg >= 60: return 'D'
        else:           return 'F'
    
    def get_grade_for_subject(self, subject):
        """Return letter grade for a specific subject score."""
        score = self.grades.get(subject, 0)
        if score >= 90:   return 'A'
        elif score >= 80: return 'B'
        elif score >= 70: return 'C'
        elif score >= 60: return 'D'
        else:             return 'F'
    
    def print_report(self):
        """Display a formatted grade report for this student."""
        print(f"\n{'='*45}")
        print(f"  Student Report")
        print(f"  Name: {self.name}")
        print(f"  ID:   {self.student_id}")
        print(f"{'='*45}")
        
        if not self.grades:
            print("  No grades recorded yet.")
        else:
            print(f"  {'Subject':<20} {'Score':>6}  {'Grade':>5}")
            print(f"  {'-'*37}")
            for subject, score in sorted(self.grades.items()):
                letter = self.get_grade_for_subject(subject)
                print(f"  {subject:<20} {score:>6.1f}  {letter:>5}")
            print(f"  {'-'*37}")
            avg = self.get_average()
            letter = self.get_letter_grade()
            print(f"  {'AVERAGE':<20} {avg:>6.1f}  {letter:>5}")
        
        print(f"{'='*45}")
    
    def __str__(self):
        return f"{self.name} (ID: {self.student_id}) — {len(self.grades)} subjects, Avg: {self.get_average():.1f} ({self.get_letter_grade()})"

class GradeManagementSystem:
    """Manages a collection of students and their grades."""
    
    def __init__(self):
        self.students = {}   # {student_id: Student object}
    
    def add_student(self, name, student_id):
        """Add a new student to the system."""
        if student_id in self.students:
            print(f"  ✗ Student ID '{student_id}' already exists")
            return False
        self.students[student_id] = Student(name, student_id)
        print(f"  ✓ Added student: {name} (ID: {student_id})")
        return True
    
    def find_student(self, student_id):
        """Find a student by ID. Returns None if not found."""
        return self.students.get(student_id, None)
    
    def add_grade(self, student_id, subject, score):
        """Add a grade for a student."""
        student = self.find_student(student_id)
        if student is None:
            print(f"  ✗ No student with ID '{student_id}'")
            return False
        return student.add_grade(subject, score)
    
    def get_class_average(self):
        """Calculate the average across all students."""
        if not self.students:
            return 0.0
        averages = [s.get_average() for s in self.students.values() if s.grades]
        return sum(averages) / len(averages) if averages else 0.0
    
    def print_all_reports(self):
        """Print reports for all students."""
        if not self.students:
            print("  No students in the system.")
            return
        for student in self.students.values():
            student.print_report()
    
    def print_class_summary(self):
        """Print a summary of all students."""
        if not self.students:
            print("  No students in the system.")
            return
        
        print(f"\n{'='*55}")
        print(f"  CLASS SUMMARY")
        print(f"{'='*55}")
        print(f"  {'Name':<20} {'ID':<10} {'Avg':>6}  {'Grade':>5}")
        print(f"  {'-'*51}")
        
        grade_counts = {'A': 0, 'B': 0, 'C': 0, 'D': 0, 'F': 0}
        
        for student in self.students.values():
            letter = student.get_letter_grade()
            grade_counts[letter] += 1
            avg = student.get_average()
            print(f"  {student.name:<20} {student.student_id:<10} {avg:>6.1f}  {letter:>5}")
        
        print(f"  {'-'*51}")
        class_avg = self.get_class_average()
        print(f"  {'CLASS AVERAGE':<30} {class_avg:>6.1f}")
        print(f"\n  Grade Distribution:")
        for grade, count in grade_counts.items():
            bar = "█" * count
            print(f"    {grade}: {bar} ({count})")
        print(f"{'='*55}")

def get_valid_input(prompt, input_type=str, min_val=None, max_val=None):
    """Keep asking until we get valid input."""
    while True:
        try:
            value = input_type(input(prompt).strip())
            if min_val is not None and value < min_val:
                print(f"  Value must be at least {min_val}")
                continue
            if max_val is not None and value > max_val:
                print(f"  Value must be at most {max_val}")
                continue
            return value
        except ValueError:
            print(f"  Invalid input. Please enter a valid {input_type.__name__}.")


def main():
    system = GradeManagementSystem()
    
    print("╔══════════════════════════════════════╗")
    print("║   Student Grade Management System    ║")
    print("║         AiTechWorlds Academy         ║")
    print("╚══════════════════════════════════════╝")
    
    while True:
        print("\n┌─────────── MAIN MENU ───────────┐")
        print("│  1. Add new student              │")
        print("│  2. Add/update grade             │")
        print("│  3. View student report          │")
        print("│  4. View all student reports     │")
        print("│  5. View class summary           │")
        print("│  6. Exit                         │")
        print("└──────────────────────────────────┘")
        
        choice = input("Select option (1-6): ").strip()
        
        if choice == "1":
            print("\n── Add New Student ──")
            name = input("  Student name: ").strip()
            if not name:
                print("  ✗ Name cannot be empty")
                continue
            sid = input("  Student ID: ").strip().upper()
            if not sid:
                print("  ✗ Student ID cannot be empty")
                continue
            system.add_student(name, sid)
        
        elif choice == "2":
            if not system.students:
                print("\n  No students yet. Add a student first.")
                continue
            print("\n── Add Grade ──")
            print("  Current students:")
            for sid, student in system.students.items():
                print(f"    {sid}: {student.name}")
            sid = input("  Enter student ID: ").strip().upper()
            subject = input("  Subject name: ").strip()
            if not subject:
                print("  ✗ Subject cannot be empty")
                continue
            score = get_valid_input("  Score (0-100): ", float, 0, 100)
            system.add_grade(sid, subject, score)
        
        elif choice == "3":
            if not system.students:
                print("\n  No students yet.")
                continue
            print("\n── Student Report ──")
            sid = input("  Enter student ID: ").strip().upper()
            student = system.find_student(sid)
            if student:
                student.print_report()
            else:
                print(f"  ✗ No student with ID '{sid}'")
        
        elif choice == "4":
            print("\n── All Student Reports ──")
            system.print_all_reports()
        
        elif choice == "5":
            print()
            system.print_class_summary()
        
        elif choice == "6":
            print("\n  Goodbye! All data will be cleared.")
            break
        
        else:
            print("  ✗ Invalid option. Please enter 1-6.")


if __name__ == "__main__":
    main()

╔══════════════════════════════════════╗
║   Student Grade Management System    ║
║         AiTechWorlds Academy         ║
╚══════════════════════════════════════╝

Select option (1-6): 1
── Add New Student ──
  Student name: Alice Johnson
  Student ID: S001
  ✓ Added student: Alice Johnson (ID: S001)

Select option (1-6): 2
── Add Grade ──
  Current students:
    S001: Alice Johnson
  Enter student ID: S001
  Subject name: Mathematics
  Score (0-100): 92
  ✓ Added: Mathematics = 92.0

Select option (1-6): 5

═══════════════════════════════════════════════════════
  CLASS SUMMARY
═══════════════════════════════════════════════════════
  Name                 ID           Avg  Grade
  ───────────────────────────────────────────────────
  Alice Johnson        S001         92.0      A

  CLASS AVERAGE                    92.0

  Grade Distribution:
    A: █ (1)
    B:  (0)
    C:  (0)
═══════════════════════════════════════════════════════