How to Limit User Input in Python

When creating interactive programs in Python, one crucial task is to limit what inputs the user can provide.

This ensures that your program handles only valid inputs and doesn’t crash or perform unwanted operations due to invalid inputs. In this tutorial, we will discuss different ways to limit user input in Python.

Step 1: Using Built-in Python Functions

You can limit user input by using the built-in raw_input() (in Python 2.x) or input() (in Python 3.x) functions. You can specify the type of input you expect from the user. For example, if you want the user to input only integers, you could use int(input()).

1
user_age = int(input("Please enter your age: "))

Step 2: Using Conditions to Validate Input

Besides using built-in functions, you can limit user input by adding conditions to verify the input. For instance, if you only want to accept input between 1 and 100, you can use the if-else block to handle the validation:

1
2
3
4
5
6
user_input = int(input("Enter a number between 1 and 100: "))
 
if user_input < 1 or user_input > 100:
    print("Invalid input!")
else:
    print("Valid input!")

Step 3: Creating a Loop for Continual Input Validation

It’s also common to combine limiting input with loops to continually prompt for input until a valid one is provided:

1
2
3
4
5
6
while True:
    user_input = int(input("Enter a number between 1 and 100: "))
    if 1 <= user_input <= 100:
        break
    else:
        print("Invalid input! Try Again.")

Step 4: Handling Inputs through Exception Handling

Another way to limit input is through exception handling. Whenever there’s a run-time error due to the wrong type of user input, Python raises an exception, which you can catch and handle:

1
2
3
4
5
6
while True:
    try:
        user_input = int(input("Enter a number: "))
        break
    except ValueError:
        print("That's not a valid number! Try Again.")

Conclusion

For an effective and user-friendly Python application, it is essential to control and limit the user’s inputs. This protects the system and improves the user experience.

By using built-in functions, loops, and exception handling, developers can ensure their applications interact correctly and smoothly with users.