我如何阻止我的python程序崩溃

Question

I wrote a program to calculate the factorial of a number all work perfectly but crashes when for test I enter a float number. My goal is for a floating number to be accepted but not calculated. As the program will accept but return something like "Bad entry, only integers are accepted." I have tried multiple statement but it only work for the number I put in the statement. So I thought maybe something should be built, maybe by naming some floats and doing some sort of subtraction. But I get lost. here is the program I have so far without the floating statement included:

    def main():
# take input from the user
        num = int(input("Enter a number: "))
        factorial = 1
        if num > 100:
            print("Bad entry. It should be an integer less than or equal to 100!")
            print("Please try again: ")
        elif num == 0:
            print("The factorial of 0 is 1")
        elif num < 0:
            print("Bad entry. It should be an integer superior than or equal to 0!")
            print("Please try again: ")  
        else:
            for i in range(1,num + 1):
                factorial = factorial*i
            print("The factorial of",num,"is",factorial)

main()

Answer 1

You should use a try/catch block, since int('3.2') (or any other float string) will raise an error. For example:

try: num = int(input('Enter a number...'))
except ValueError:
   print 'We only accept integers.'
   return

Answer 2

As many have suggested, you should use a try/except block. However if you want to accept user input like "6.12" and just calculate from the integer part, you should do:

user_in = "6.12" # or whatever the result from the input(...) call is
user_in = int(float(user_in)) # 6

int cannot operate on a string that's not integer-like, but it CAN operate on a floating point number. Calling float on the string will give you a floating point number, and calling int on that floating point number will return the integer part.

Answer 3

def main():
    # take input from the user
    num = float(input("Enter a number: "))
    if (num%1 != 0):
        print("Bad entry, only integers are accepted.")
        return 

    num = int(num)
    factorial = 1
    if num > 100:
        print("Bad entry. It should be an integer less than or equal to 100!")
        print("Please try again: ")
    elif num == 0:
        print("The factorial of 0 is 1")
    elif num < 0:
        print("Bad entry. It should be an integer superior than or equal to 0!")
        print("Please try again: ")  
    else:
        for i in range(1,num + 1):
            factorial = factorial*i
        print("The factorial of",num,"is",factorial)

main()