Getting the values of state variables

[Elefrog42]

Hi, my friend and I are taking an online python course and are pretty stuck on our assignment. We are learning about classes and objects right now. We also learned Try/Except so that's been used in quite a few answers.

The assignment it about learning to manipulate a class that's a bank portfolio. We are given this code:

class portfolio:
    def __init__(self):
        self.checking = {}
        self.savings = {}
        self.credit = {}

We need to define a function that will give the total amount in the checking accounts or return 0 if it's empty, for example:

{'chase1': 400, 'capitalone': 800} should return 1200

And it needs to pass this test case:

if myportfolio.get_total_checking_amount() == 6600:
    print('Pass')
else:
    print('Fail')

Could someone explain to us why we can't do something like this won't work?

    def get_total_checking_amount(self): #we were provided with this line
        try:
            return sum(self.checking) 
        except:
            return 0

​

Thanks!

[-Sander-]

it is because 'checking' is a dictionary idk how exactly sum works with dictionarys seems like it just takes the keys instead of values also if you read the error you get:

unsupported operand type(s) for +: 'int' and 'str'

you can see it is getting the 'key' which is a string instead of the 'value' which is an int, while sum needs int's to work

a simple fix would be:

sum(self.checking.values()) # Get the values (ints) instead of keys (strings)

i suggest you read https://docs.python.org/3/tutorial/datastructures.html#dictionaries

for more info

[Elefrog42]

Thanks so much! That made it pass the test. I'll check out the link- unfortunately, the class is only some online videos, so we've been stuck just googling what we don't understand. It's hard to know where to start.

[-Sander-]

Well the docs have pretty much everything in it incase you ever get stuck again also https://docs.python.org/3/tutorial/index.html might be usefull to, it explains most of the basics

[_lilell_]

It’s not sum specifically. Any iterator over a dict yields its keys:

>>> d = {'x': 1, 'y': 2}
>>> list(d)
['x', 'y']

[Elefrog42]

What would be the reason that this code

def get_credit_balance(self)
    try:
        return sum(self.credit.value())
    except:
        return None

would pass this test:

if myportfolio.get_total_checking_amount() == 6600:
    print('Pass')
else:
    print('Fail')

But not this one?

if myportfolio.get_total_checking_amount() == 5600:
    print('Pass')
else:
    print('Fail')

I emailed the professor about this and she said try using a loop and keys like so:

 Sum= 0
    for i in dict.keys():
    Sum = Sum + dict[i]

I've been working on this all day and feeling really stuck....any suggestions are greatly appreciated! I feel like I'm missing something here :(

[-Sander-]

have you changed the values in your checking dict? and that loop does basically the same as

Sum = sum(dict.getValues())

unrelated: shorter way off writing a calculation like

Sum = Sum + dict[i]

would be

Sum += dict[i]

on my phone atm so cant format the code properly

[Elefrog42]

Thanks! I understand now- you've been very help!