# what is scope in python

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Scope
Variables can only reach the area in which they are defined, which is called scope. Think of it as the area of code where variables can be used. Python supports global variables (usable in the entire program) and local variables.

By default, all variables declared in a function are local variables. To access a global variable inside a function, it’s required to explicitly define ‘global variable’.

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Example
Below we’ll examine the use of local variables and scope. This will not work:

but this will:

Let’s examine this further:

Calling functions in functions
We can also get the contents of a variable from another function:

If a variable can be reached anywhere in the code is called a global variable. If a variable is known only inside the scope, we call it a local variable.

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Carl Wainwright Sun, 28 Aug 2016

I ran this code in v2.7.10 and it executed without any errors

`def f(x,y):    print('You called f(x,y) with the value x = ' + str(x) + ' and y = ' + str(y))    print('x * y = ' + str(x*y))    z = 4 # cannot reach z, so THIS WON'T WORK    print(z)z = 3f(3,2)`

`MacBookAir:.ssh carlwainwright\$ python ~/Projects/Python/helloworld.py You called f(x,y) with the value x = 3 and y = 2x * y = 64`

Frank Sun, 28 Aug 2016

Try this program:

`def showz():    print(z)def f(x,y):    print('You called f(x,y) with the value x = ' + str(x) + ' and y = ' + str(\$    print('x * y = ' + str(x*y))    z = 4 # cannot reach z, so THIS WON'T WORK    print(z)z = 3f(3,2)showz()`

In this example z will still be 3 after calling f(3,2). Sorry for the confusion, ill update

Carl Wainwright Mon, 29 Aug 2016

So without "global z" in function 'f' z is local to the function and when you return back the global z is scoped.

Frank Wed, 31 Aug 2016

Correct, otherwise the changed occur only locally

Greg Sun, 23 Jul 2017

To follow up on Carl's comment, the supplied example in the tutorial (with the bold, italic "this will not work") also works fine for me in Python 3.6. I thought I'd let everyone know what I discovered while experimenting to find what would and would not work.

Without using the keyword 'global'...

You can reference a global variable inside a function. This code works fine, and prints the global value of z (10) twice:

`def testing_scope():    print(z)z = 10testing_scope()print(z)`

You can also create a local variable with the same name inside a function. This code works fine, and prints the local value of z (1) followed by the global value of z (10):
`def testing_scope():    z = 1    print(z)z = 10testing_scope()print(z)`

However, you cannot first reference global variable then create a local variable with the same name. Trying to define testing_scope like this does not work:
`def testing_scope():    print(z)    z = 1`

I hope that helps clarify things!

Greg Sun, 23 Jul 2017

My apologies for the indentation not showing up properly. I would edit if I could.

Frank Wed, 26 Jul 2017

No problem, all indented correctly now :)