How to change a global variable in python?

Question

I am accessing data from different accounts from an online platform over their API. I have created a class called Account that holds all the information necessary to access this API. I want to be able to set the account (and the necessary info to gain access) each time before I make an API request. I tried to make a function that will set a global variable Acct to the proper account class instance but after I call choose_account(), Acct continues to return '', is there a better way to handle this type of procedure?

Acct = ''
def choose_account():
    global Acct
    get = raw_input(r'Adap1, Adap2, Adap3, or Adap4? ')
    if get == 'Adap1':
        Acct = Adap1
    elif get == 'Adap2':
        Acct = Adap2
    elif get == 'Adap3':
        Acct = Adap3
    elif get == 'Adap4':
        Acct = Adap4
    else:
        print ("Please type Adap1, Adap2, Adap3, or Adap4 ")

Edit: show Account and Adap1 etc

class Account():

    def __init__(self, name, username, password, org_id):
        self.name = name
        self.username = username
        self.password = password
        self.org_id = org_id

    def update_pw(self, pw):
        self.password = pw 

Adap1 = Account('Adap1', 'username', 'password', 'org_id')

where are you setting Adap1,2,3, and 4? They look like they're empty from that code. — SirParselot
– SirParselot, Commented Aug 21, 2015 at 16:27
How are you defining Adap1, Adap2, Adap3, Adap4? Right now you are treating them as variables in your assignment Acct = Adap1, but I suspect you may have wanted to assign Acct to the string 'Adap1'? — scrappedcola
– scrappedcola, Commented Aug 21, 2015 at 16:27
But if that's the case, you could just do Acct = get if get in ('Adap1', ...) else None. — Kevin
– Kevin, Commented Aug 21, 2015 at 16:28
Good point @Kevin but I wan't to set the value of Acct to a class instance of Account so it doesn't work haha — bpr
– bpr, Commented Aug 21, 2015 at 16:30
If you don't mean to have Adap1, Adapt2... be strings and they are indeed defined somewhere else, then you need to either pass them into your choose_account() fuction, or have them be global as well — ThatGuyRussell
– ThatGuyRussell, Commented Aug 21, 2015 at 16:31

holdenweb · Accepted Answer · 2015-08-21 16:42:09Z

4

Sorry, but use of global variables in that way is not usually a good way to go. You are probably new to programming, so I don't want you to feel you are being "told off", but it would be much more sensible to have the function return a value, and then set the global variable with a statement like

Acct = choose_account()

In which case your function ought to look more like this (untested code):

def choose_acct():
    while True:
        get = raw_input(r'Adap1, Adap2, Adap3, or Adap4? ')
        if get == "Adap1":
            return Adap1
        elif get == "Adap2":
            return Adap2
        elif get == "Adap3":
            return Adap3
        elif get == "Adap4":
            return Adap4

Better still, you could consider a data-driven approach to the problem, and define a dictionary like

adict = {"Adap1": Adap1, "Adap2": Adap2, "Adap3": Adap3, "Adap4": Adap4}

Then your function could read (again, untested)

def choose_acct():
    while True:
        get = raw_input(r'Adap1, Adap2, Adap3, or Adap4? ')
        result = adict.get(get, None)
        if result:
            return result

As your experience level grows you will start to recognise the difference between good and bad code, but you made a pretty good attempt.

answered Aug 21, 2015 at 16:42

holdenweb

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3 Comments

bpr Over a year ago

Thanks, really appreciate the feedback!

bpr Over a year ago

I see this "while True:" line in a lot of code but I am not really sure why it is necessary or what advantage it brings, would you mind explaining that to me a bit?

Jake Griffin Over a year ago

Typically, you will see while True: when you want a piece of code to never terminate or accompanied by a break or return inside the loop (like in this case). It's just a way to repeat a set of commands over and over. Some might recommend against using it with a break or return (and just having the break/return condition be what replaces the True), but sometimes while True: just results in more readable code, which is a very good thing in my opinion.

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