[Tutor] User defined exceptions

[Manprit Singh]

Dear Sir,

I have written an example on user defined exceptions, just to check if my
understanding is correct, I request you to read the points and  let me know
if those are correct or not


class MarksError(Exception):   # A simple user defined exception
    pass

def grades(glist, score):
    if score < 0 or score > 100:
        raise MarksError("Invalid Score")    # Argument to raise is an
exception instance
    for ch, rg in glist:
        if score < rg:
            return ch

lst = [("F", 60),
       ("D", 70),
       ("C", 80),
       ("B", 90),
       ("A", 101)]


try:
    marks= int(input("Enter marks"))
    grade = grades(lst, marks)

except MarksError as err:
    print(err)

else:
    print(f'for {marks} marks the grade is {grade}')

This program is for printing the grade of a student  based on marks .

1) In the starting, I have written a very simple user-defined Exception
class- MarksError, simply placing a pass inside this class causes no extra
addition, this class inherits everything from the Exception class.

2) Inside the function def grades, i have  used raise keyword to raise an
exception . Just besides the raise keyword I have written
MarksError("Invalid Score"), which is basically an instance of the
exception class MarksError with the argument "Invalid Score".

3) In the except block given below:
except MarksError as err:
    print(err)
variable err is bound to the exception instance written with raise keyword,
hence print(err)  will print the argument "Invalid Score", when exception
is handled.

Kindly comment

Regards
Manprit Singh