陷入无限循环。 Python

Question

I am trying to make this code run so that when I enter 'done' it break me out of the loop. The issue is I put a try/except to try and catch anything that isn't a number and feed back and error message. This catches before the if statement that would break me out of the loop and instead feeds back an error message and catches me in an infinite loop. I've tried moving the try/except after all the if/else statements but then the string gets placed inside the value for maximum and this is not what I am trying to accomplish. Is there a way for me to get the try and except to run but still allow me to pass a 'done' command to exit the loop?

largest = None
smallest = None

while True:
    num = input("Enter a number: ")
    try:
        num = float(num)
    except:
        print('Invalid Input')
        continue
    if num == "done" :
        break
    elif largest is None:
        largest = num
    elif smallest is None:
        smallest = num
    elif largest < num:
        largest = num
    elif smallest > num:
        smallest = num

    print(num)

print("Maximum", largest)
print("Minimum", smallest)

Answer 1

first test for done and then convert to float

And you can simplify the tests

The program should work if you enter none or one number

    num = input("Enter a number: ")
    if num == "done" :
        break
    try:
        num = float(num)
    except:
        print('Invalid Input')
        continue
    largest = largest or num
    smallest = smallest or num
    largest = max(num, largest)
    smallest = min(num, smallest)

Answer 2

Change this:

try:
    num = float(num)
except:
    print('Invalid Input')
    continue

if num == "done":
    break

to this:

try:
    num = float(num)
except:
    if num == "done":
        break

    print('Invalid Input')    
    continue

By putting the if inside the except , you allow the loop to break before it can continue .

Answer 3

The reason is that you're using checking if the input is a float before you're checking for "done" so when it's actually "done" it just continues before it checks for it.

I would fix it this way.

largest = None
smallest = None

while True:
    num = input("Enter a number: ")

    # check if it's done first
    if num == "done" :
        break

    try:
        num = float(num)
    except:
        print('Invalid Input')
        continue

    elif largest is None:
        largest = num
    elif smallest is None:
        smallest = num
    elif largest < num:
        largest = num
    elif smallest > num:
        smallest = num

    print(num)

print("Maximum", largest)
print("Minimum", smallest)