Reverse number in Python-CodePudding

I have a homework to make a program that can reverse an input number, but have a requirement to return a sentence with no error when the input is not a number (i.e. words or sentence). For example, when I input abc the program will return Error, please input a number! How can I make it return a sentence when input a str This is the code I've done so far.

def reverse_num(x):
    x = num
    x = str(x)
    
    if x[0] == '-':
        a = x[::-1]
        return f"{x[0]}{a[:-1]}"
    else:
        return x[::-1]

num = input("Enter an integer (positive or negative): ")
print (reverse_num(num))

Noted that the requirement is to reverse both positive and negative number with cannot be return str, but my code return all of them in reversed.

CodePudding user response：

Let's Break Your Problem in 2 Function:

A function to reverse and a loop to read until you get a number or user cancels:



    def reverse_input(num):
        if num[0] == "-":
            temp = num[:0:-1]
            return (-int(temp))
        return int(num[::-1])
    
    while True:
        num = input("Enter Number")
        if num[0] == "-":
            flag = num[1:].strip().isdigit()
        else:
            flag = num[:].strip().isdigit()
        if flag:
            print("User input is Number")
            print(reverse_input(num))
            break
        else:
            print("User input is string")
            resp = input("Would You like to try Again? Enter Y to try and N to Cancel")
            if resp == 'n' or resp == 'N':
                print("Sorry Execute Again")

What does it do ?

It reads input from user. Input returns string always.
First, we check if Entered String had negation sign or not. If it is there we'll test string skipping negation sign. Otherwise, we will use whole string.
We will check if entered string is number using built-in isdigit() function. And Call function to get reversed string.
Function will reverse string and typecast to integer with sign.

CodePudding user response：

You may use try-except statements

try:
    x = int(num)
    x = str(x)
    #rest
except ValueError:
     #error message