FAQ
overflow

QUESTION

A global variable created in one function cannot be used in another function directly. Instead I need to store the global variable in a local variable of the function which needs its access. Am I correct? Why is it so?

ANSWER

You can use a global variable in other functions by declaring it as global in each function that modifies it:

globvar = 0

def set_globvar_to_one():
    global globvar    # Needed to modify global copy of globvar
    globvar = 1

def print_globvar():
    print globvar     # No need for global declaration to read value of globvar

set_globvar_to_one()
print_globvar()       # Prints 1

I imagine the reason for it is that, since global variables are so dangerous, Python wants to make sure that you really know that's what you're playing with by explicitly requiring the global keyword.

See other answers if you want to share a global variable across modules.

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