Why Does My Recursive Input Validation Function Return None Instead of 'a' or 'b'?

Recursive Function Returning None: Problem and Solution

Problem:

A recursive function designed to validate user input and return "a" or "b" is unexpectedly returning None when incorrect input is provided and then corrected.

Function Code:

def get_input():
    my_var = input('Enter "a" or "b": ')

    if my_var != "a" and my_var != "b":
        print('You didn\'t type "a" or "b". Try again.')
        get_input()
    else:
        return my_var

Expected Behavior:

When the user inputs valid input ("a" or "b"), the function should return the value of my_var.

Actual Behavior:

When the user inputs invalid input and then enters "a" or "b", the function returns None instead of the valid input value.

Reason:

In the recursive call within the if statement:

get_input()

The return value of the recursive call is not being returned by the function. Instead, the function falls off the end without explicitly returning anything. In Python, falling off the end of a function implicitly returns None.

Solution:

To fix this issue, return the recursive call's return value within the if statement:

if my_var != "a" and my_var != "b":
    print('You didn\'t type "a" or "b". Try again.')
    return get_input()

This ensures that when invalid input is provided and corrected, the function correctly returns the value of my_var, as intended.

The above is the detailed content of Why Does My Recursive Input Validation Function Return None Instead of 'a' or 'b'?. For more information, please follow other related articles on the PHP Chinese website!