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pythonfunctionglobal-variablesdeclaration
alwbtc
alwbtc

Reputation: 29495

Global variable in Python

I've been reading a Python textbook, and I see the following code:

class Database:
# the database implementation
    pass

database = None

def initialize_database():
    global database
    database = Database()

Now, why is there a global declaration inside initialize_database function? We had defined database outside the function, doesn't it make it global already?

Best Regards,

Upvotes: 3

Views: 773

Answers (2)

Nathan
Nathan

Reputation: 6225

'global x' doesn't make x global, it should be read as "from now on in this namespace, treat all references to x as as references to x in a higher namespace."

Remember you're not permanently doing anything to x, your just making x point to something different within a function.

Upvotes: 1

icktoofay
icktoofay

Reputation: 129119

You can reference a global when it's not declared global in a function, but you can only read it; writing it will create a new local variable hiding the global variable. The global declaration makes it able to write to the global.

Upvotes: 9

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