python) how to solve this nontype problem?

Question

def manage_account(balance, choice, money):
    if choice == '+':
        balance = balance + money
        return balance
    elif choice =='-':
        if balance > money:
            balance= balance - money
            return balance
        elif balance < money:
            print('There is not enough money in your account')
    else:
        print('ERROR')

balance = 10000    
balance = manage_account(balance, '-', 20000)
balance = manage_account(balance, '-', 5000)
balance = manage_account(balance, '=', 20000)
balance = manage_account(balance, '+', 1000)

why nontype problem happened? Ans how can i escape this awful situation?

Your function lacks a `return` statement. Hence it returns None. — Jonathan Scholbach, Sep 28 '21 at 11:20
Does [this](https://stackoverflow.com/a/67439738/10952503) help you ? (other another answer) — Elikill58, Sep 28 '21 at 11:22
A hint for you next question: Please always include the error message you get. In this case it was quite easy to spot your problem, but in future this helps others help you. — Jonathan Scholbach, Sep 28 '21 at 11:26
And another hint: Try to reduce your code to a minimum example: https://stackoverflow.com/help/minimal-reproducible-example And you could use a debugging technique, such as using `breakpoint()`. — Jonathan Scholbach, Sep 28 '21 at 11:27

Jonathan Scholbach · Answer 1 · 2021-09-28T11:29:10.043

Your function lacks a return statement, for the case that the account amount gets negative. Then it returns None.

That is why balance = manage_account(balance, '-', 20000) is None, and when you call the function the second time, an error is raised at balance - money. An analogue problem occurs when passing '=' as parameter choice to the function a couple of lines below.

Depending on what is the desired behavior of your function, you should consider using a raise ValueError instead of printing Error.

python) how to solve this nontype problem?

1 Answers1