been working on this for hours, thought i had it down but it turns out i have it all wrong.
The assignment is to
Write a program that computes your sem
I used some things that might come in handy in the future, if you continue to program in python (like generators, list comprehension, map) 
You can try something like this: (Can be simplified, but for clarity.. ) 
#!/bin/env python3
"""
Course grade computation
"""
# quiz.py
import sys
def take(name="", dtype='int', sentinel=-1):
    """:param dtype: string representing given input type"""
    counter = 0
    i = 0
    while True:
        i = eval(dtype)(input("{} #{}: ".format(name,counter)))  # We should use function map instead, but for simplicity...
        if i > 10 or i < -1:
            print("Invalid input: input must be in range(0,10) or -1", file=sys.stderr)
            continue
        if i == sentinel:  # <-- -1 will not be added to list
            break
        yield i
        counter += 1
def main():
    grades_map = dict([(100, 'A'), (90, 'B'), (80, 'C'), (70, 'D'), (60, 'F')])
    print("Input quiz scores")
    quizes = [i for i in take("Quiz", dtype='float')]
    quiz_sum = sum(quizes)
    quiz_lowest = min(quizes)
    print("Input project scores")
    projects = [i for i in take("Project", dtype='float')]
    proj_sum = sum(projects)
    print("Input exam scores")
    exam1, exam2, final = map(float, [input("Exam #1:"), input("Exam #2:"), input("Final:")])
    total = ...  # Didn't know what the total really is here
    average = ...  # And same here
    grade = grades_map[round(average, -1)]
    # Handle your prints as you wish
if __name__ == '__main__':
    main()
EDIT: Change in the generator so that -1 is not added to the list