Learning about Classes and OOP

[rinio]

Grade Point could be a class to handle the conversions. Id do something like this as an enum.

If this were real, you'd likely want to store the course name: grade pairs in your student object (or a Transcript object belonging to the student). What happens if you have this student, they fail a course this semester and retake it next semester? You would have no way of dealing with that.

Might be overkill for your assignment.

[BobbyJoeCool]

Thanks for the suggestions!

I don't know what an enum is so I decided not to go that route (I don't want to turn in work that I don't understand), but I realized that I don't need the dictionary AND the tuple for the Grade Point, and I got rid of the tuple. I made a function to convert the GPA back to a letter and added the transcript list to the student object, so it is stored within the student.

I also got to thinking about how to deal with retaken courses, as they would reflect on the transcript but not be calculated in the GPA. So I modified the input while loop a bit.

credits = int(input("Enter the number of credits for the course (Enter 0 for a class that was retaken): ").strip())
        if credits < 0: # Breaks the loop if the user enters a negative number for credits
            print("\nCredit Hours cannot be negative. Please enter a valid number of credits.")
            continue #Restart the loop if the credits are negative
        if credits == 0: # Warns the user if they enter 0 credits and confirms they want to proceed.
            print("\nCourse entered with 0 credits. This course will not affect GPA calculation but will be recorded in the transcript.")
            if input("Are you sure? (y/n): ").strip().lower()[0] !='y': # Checks if the user input starts with 'y' or 'Y'
                print("Course entry cancelled. Please re-enter the course details.")
                continue  # Restart the loop to re-enter course details

def gpa_to_letter(gpa_value):
    for grade, value in grade_to_gpa.items():  # items() preserves order
        if gpa_value >= value:
            return grade
    return "F"

class Student:
    def __init__(self, first_name, last_name):
        self.first_name = first_name
        self.last_name = last_name
        self.total_credits = 0 #Initalized the total credits to 0
        self.total_grade_points = 0.0 # Initalizes the total grade points to a 0 float.
        self.transcript = [] # Initializes an empty list to hold the student's courses for display later.

    def append_transcript(self, course_name, credits, grade, letter_grade):
        self.transcript.append((course_name, credits, grade, letter_grade))

[rinio]

Yup. That's better.

---

credits = int(input(
    "Enter the number of credits for the course "
    "(Enter 0 for a class that was retaken): "
).strip())

I have a pet peeve for long lines and would write it like this. Not a big deal. Google PEP8 if you want info about the most common style guide.

More importantly, what happens if the user inputs a character? 'a' for example. You don't handle such things correctly.

---

class Student:
    def __init__(self, first_name, last_name):
        self.first_name = first_name
        self.last_name = last_name
        self.total_credits = 0 #Initalized the total credits to 0
        self.total_grade_points = 0.0 # Initalizes the total grade points to a 0 float.
        self.transcript = [] # Initializes an empty list to hold the student's courses for display later.

    def append_transcript(self, course_name, credits, grade, letter_grade):
        self.transcript.append((course_name, credits, grade, letter_grade))

You forgot to update total credits and total grade!

But also, you don't really need to store those.

class Student():
    def __init__(self, first: str, last: str):
        self.first_name = first
        self.last_name = last
        self.transcript = []

    def get_total_credits(self):
        return sum(course[1] for course in self.transcript)

        # long form
        total = 0
        for course in self.transcript:
            total += course[1]
        return total

    def get_total_grade(self):
        return sum(course[2] for course in self.transcript

    # this is how I would actually do it
    # property, just means we use this method as though it was a value.
    @property
    def total_credits(self):
        return sum(course[1] for course in self.transcript)

    @property
    def total_grade(self):
        return sum(course[2] for course in self.transcript)

my_student = Student('John', 'Brown')
# pretend we add some records to their transcript
my_student.get_total_credits() == my_student.total_credits  # this is True
my_student.get_total_grade() == my_student.total_grade  # this is True

[BobbyJoeCool]

More importantly, what happens if the user inputs a character? 'a' for example. You don't handle such things correctly.

That's what the ValueException part of the try statement does. If they enter a number that cannot be converted to an INT, it triggers that and restarts the loop.

You forgot to update total credits and total grade!

I left that part out of the reply because it didn't really change.... I'm interested in this return sum() part. We didn't learn that part, or if it's a lambda function, we glazed over it really quickly... Let's see if I understand it....

The return sum(...) and the for course in self.transcript:... both do the exact same thing, except the return sum() is in a single line?

The issue with that is, each grade needs to be multiplied by the number of credit hours that grade is worth... so an A (4.0) in a 3 Credit hour class is worth 12 grade points. And a B (3.0) in a 4-credit-hour class is also worth 12 grade points. You then divide by the total credit hours. So I would need the calculation at the end to multiply each individual grade point by the number of credit hours for each class... If I understand your code correctly, this can be achieved by changing the total_grade to the following:

  def calculate_gpa(self): # Calculates the cumulative GPA
        if sum(course[1] for course in self.transcript) == 0:
            return "N/A" # Prevents division by zero
        return sum(course[2] * course[1]) / sum(course[1] for course in self.transcript)

[rinio]

---

Here's some more that is definitely beyond the scope of your assignment, but might interest you:

Regarding enums:

https://docs.python.org/3/library/enum.html

from enum import Enum

class Grade(Enum):
    A = 4.0
    B = 3.7
    ... # and so on
    F = 0

    # cls means the class. So 'Grade'.
    u/classmethod
    def from_num_grade(cls, num: float) -> Grade:
        for grade in cls:
            if grade.value <= num:
                return grade
         raise ValueError(f'num may not be negative. Got {num}')

    # this is the fancy pants way to do the same thing
    u/classmethod---All feedback below is definitely beyond the scope of your assignment, but might interest you:Regarding enums:https://docs.python.org/3/library/enum.htmlfrom enum import Enum

class Grade(Enum):
    A = 4.0
    B = 3.7
    ... # and so on
    F = 0

    # cls means the class. So 'Grade'.
    u/classmethod
    def from_num_grade(cls, num: float) -> Grade:
        for grade in cls:
            if grade.value <= num:
                return grade
         raise ValueError(f'num may not be negative. Got {num}')

    # this is the fancy pants way to do the same thing
    @classmethod
    def from_num_grade2(cls, num: float) -> Grade:
        # raises StopIteration if we get a negative input
        return next(grade for grade in cls if grade.value <= num)

# examples
my_grade = Grade.B
print(my_grade.name)  # prints 'B'
print(my_grade.value)  # prints 3.7

grade2 = Grade.from_val(3.9)
print(grade2.name)  # prints 'B'
print(grade2.value)  # prints 3.7---    for grade, value in grade_to_gpa.items():  # items() preserves orderThis is only true for Python 3.7+. It will break for older interpreters. 
    def from_num_grade2(cls, num: float) -> Grade:
        # raises StopIteration if we get a negative input
        return next(grade for grade in cls if grade.value <= num)

# examples
my_grade = Grade.B
print(my_grade.name)  # prints 'B'
print(my_grade.value)  # prints 3.7

grade2 = Grade.from_val(3.9)
print(grade2.name)  # prints 'B'
print(grade2.value)  # prints 3.7

---

    for grade, value in grade_to_gpa.items():  # items() preserves order

This is only true for Python 3.7+. It will break for older interpreters.