for循环内的Python While循环在值无效时继续重复

Question

This is my code:

for i in range(1, 5):
    try:
        grade = int(input("Please enter {}'s grade for practical assessment {}: ".format(name, i)))
        while (grade < 0 and grade > 40):
            print("That is not a valid grade.")
            continue
    except ValueError:
        print("That is not a valid value.")
        continue

My question is that how to check if the grade is in range and to make the loop repeat if a false input is entered. When I tried to run the program, and enter an over range input, it goes to the next assessment number instead of trying again until it's true.

Answer 1

You could use something like this which uses a while True loop as well as a try statement and except clause to determine whether the user entered a valid grade:

names = ["Adam", "Bob", "Chloe"] # Example list of names

for name in names:
  for i in range(1, 5):
    while True:
      try:
        grade = int(input("Please enter {}'s grade for practical assessment {}: ".format(name, i)))
        if not (0 <= grade <= 40):
          raise ValueError()
      except ValueError:
        print("Error: Please enter a grade between 0 and 40")
      else:
        break

Example Usage:

Please enter Adam's grade for practical assessment 1:  a
Error: Please enter a grade between 0 and 40
Please enter Adam's grade for practical assessment 1:  -1
Error: Please enter a grade between 0 and 40
Please enter Adam's grade for practical assessment 1:  10
Please enter Adam's grade for practical assessment 2:  4
Please enter Adam's grade for practical assessment 3:
...

Try it here!