如何使elif语句和ValueError除外重复function？

Question

I am on section 4 of the Udemy "Automate the Boring Stuff" course, which covers handling errors with try/except.

How can I get the script to run from the beginning if the user input is an invalid non-integer or negative integer?

print('How many cats do you have?')
numCat = input()
try:
    while True:
        if int(numCat) >= 4:
            print('That is a lot of kitties')
            break
        elif int(numCat) <= -1:
            print('You can not have '+str(numCat)+' kitties, try again')
            break
        else:
            print('That is not that many kitties')
            break
except ValueError:
    print('Please enter a number, try again')

Answer 1

What's the purpose of the loop if every path has a break in it? You could do something like this:

cond = True
while cond:
    print('How many cats do you have?')
    numCat = input()
    try:
        cond = False
        if int(numCat) >= 4:
            print('That is a lot of kitties')
        elif int(numCat) <= -1:
            print('You can not have '+str(numCat)+' kitties, try again')
        else:
            print('That is not that many kitties')
    except ValueError:
        print('Please enter a number, try again')

Or either with break

while True:
    print('How many cats do you have?')
    numCat = input()
    try:
        if int(numCat) >= 4:
            print('That is a lot of kitties')
        elif int(numCat) <= -1:
            print('You can not have '+str(numCat)+' kitties, try again')
        else:
            print('That is not that many kitties')
        break
    except ValueError:
        print('Please enter a number, try again')

Answer 2

I would personally do something like this:

BONUS: isdigit only counts positive numbers!

numCat = None
while True:
  numCat = input()
  if numCat.isdigit():
     break
  print('Please enter a positive number.')
if int(numCat) >= 4:
  print('That is a lot of kitties')
else:
  print('That is not that many kitties')

Answer 3

Not sure if this is the most efficient solution or if there are better ones. But what I would do is loop through the try and let the user input again

print('How many cats do you have?')
numCat = input()
loopCount = 0
while loopCount == 0:
    numCat = input()
    try:
        while True:
            if int(numCat) >= 4:
                print('That is a lot of kitties')
                break
            elif int(numCat) <= -1:
                print('You can not have '+str(numCat)+' kitties, try again')
                break
            else:
                print('That is not that many kitties')
                break
        loopCount = 1
    except ValueError:
        print('Please enter a number, try again')

Answer 4

move your try-except block and input inside while loop to catch invalid inputs.

while True:
    print('How many cats do you have?')
    numCat = input()
    try:
        if int(numCat) >= 4:
            print('That is a lot of kitties')
            break
        elif int(numCat) <= -1:
            print('You can not have ' + str(numCat) + ' kitties, try again')
            break
        else:
            print('That is not that many kitties')
            break
    except ValueError:
        print('Please enter a number, try again')