How to make a local variable (inside a function) global [duplicate]

Question

Here are two methods to achieve the same thing:

Using parameters and return (recommended)

def other_function(parameter):
    return parameter + 5

def main_function():
    x = 10
    print(x)    
    x = other_function(x)
    print(x)

When you run main_function, you'll get the following output

>>> 10
>>> 15

Using globals (never do this)

x = 0   # The initial value of x, with global scope

def other_function():
    global x
    x = x + 5

def main_function():
    print(x)    # Just printing - no need to declare global yet
    global x   # So we can change the global x
    x = 10
    print(x)
    other_function()
    print(x)

Now you will get:

>>> 0    # Initial global value
>>> 10   # Now we've set it to 10 in `main_function()`
>>> 15   # Now we've added 5 in `other_function()`

Simply declare your variable outside any function:

globalValue = 1

def f(x):
    print(globalValue + x)

If you need to assign to the global from within the function, use the global statement:

def f(x):
    global globalValue
    print(globalValue + x)
    globalValue += 1

If you need access to the internal states of a function, you're possibly better off using a class. You can make a class instance behave like a function by making it a callable, which is done by defining __call__:

class StatefulFunction( object ):
    def __init__( self ):
        self.public_value = 'foo'

    def __call__( self ):
        return self.public_value


>> f = StatefulFunction()
>> f()
`foo`
>> f.public_value = 'bar'
>> f()
`bar`

Using globals will also make your program a mess - I suggest you try very hard to avoid them. That said, "global" is a keyword in python, so you can designate a particular variable as a global, like so:

def foo():
    global bar
    bar = 32

I should mention that it is extremely rare for the 'global' keyword to be used, so I seriously suggest rethinking your design.