local variable 'marks' referenced before assignment

[Calli]

The error i am getting is

UnboundLocalError: local variable 'marks' referenced before assignment

def main():
    totalMarks = 0
    nSubjects = 0
    while True:
        marks == input("Enter for subject " + str(nSubjects + 1) + ": ")
        if marks == '':
            break
        marks = float(marks)
        if marks < 0 or marks > 100:
            print("INVALID MARKS !!")
            continue
        nSubjects = nSubjects + 1
        totalMarks += marks

    percentage = totalMarks / nSubjects
    print("Total marks: ",int(totalMarks))
    print("Number of Subjects: ",nSubjects)
    print("Percentage: ", round(percentage, 2))

if __name__ == "__main__":
    main()

But if i set the marks to 0 the if statement is not executed

totalMarks = 0
nSubjects = 0
marks = 0

[deanhystad]

    while True:
        marks == input("Enter for subject " + str(nSubjects + 1) + ": ")

Using comparison "==" where you want to use assignment "="

[Yoriz]

You have double == which does a comparison

marks == input("Enter for subject " + str(nSubjects + 1) + ": ")

you want a single = to assign

marks = input("Enter for subject " + str(nSubjects + 1) + ": ")

[Calli]

Holly molly my eyes are getting weaker and weaker day by day :( thanks a lot fam. You're all the best