CODEWITHSUNDEEP
python-2.7
gomri15
gomri15

Reputation: 1

getting a None value and i don't know why

def getUsername():
username = raw_input("Enter Your Username: ")
if not username[0].isalpha():
    print "wrong"
    getUsername()
else:
    return username

am trying to check if the first char of the string username is a alphabetical char and if it's not to ask the user for hes user name again and if it is set it to username.

but when i run though the function more the once i get back the value None from username what i mean by that is when i run the function and give it a bad value once it works fine and asks me again for a value but when i print out the value i get back a None.

can you please tell me why.

and of course how to fix it thanks in the advance :

Upvotes: -1

Views: 48

Answers (2)

Ilja Everilä
Ilja Everilä

Reputation: 52929

You're missing a return in your recursive call to getUsername():

def getUsername():
    username = raw_input("Enter Your Username: ")
    if not username[0].isalpha():
        print "wrong"
        return getUsername()
    else:
        return username

Without it your function recursively calls getUsername(), exits the if/else block and falls off from the function, which implicitly returns None.

From the data model documentation:

None

This type has a single value. There is a single object with this value. This object is accessed through the built-in name None. It is used to signify the absence of a value in many situations, e.g., it is returned from functions that don’t explicitly return anything. Its truth value is false.

On defining functions:

The return statement returns with a value from a function. return without an expression argument returns None. Falling off the end of a function also returns None.

Upvotes: 2

Aritra Chakraborty
Aritra Chakraborty

Reputation: 12542

Why even use a recursive Function for this just use a while Loop.

def getUname():
    while True:
        username = raw_input("name:");
        if not username[0].isalpha():
            print "wrong";
        else:
            return username;

it should return the same.

Upvotes: 0

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