Python Scope

A variable is only available from inside the region it is created. This is called scope.

Local Scope

A variable created inside a function belongs to the local scope of that function, and can only be used inside that function.

def myfunc():
  x = 300
  print(x)

myfunc()

Function Inside Function

As explained in the example above, the variable x is not available outside the function, but it is available for any function inside the function:

def myfunc():
  x = 300
  def myinnerfunc():
    print(x)
  myinnerfunc()

myfunc()

Global Scope

A variable created in the main body of the Python code is a global variable and belongs to the global scope.

Global variables are available from within any scope, global and local.

x = 300

def myfunc():
  print(x)

myfunc()

print(x)

Naming Variables

If you operate with the same variable name inside and outside of a function, Python will treat them as two separate variables, one available in the global scope (outside the function) and one available in the local scope (inside the function):

x = 300

def myfunc():
  x = 200
  print(x)

myfunc()

print(x)

Global Keyword

If you need to create a global variable, but are stuck in the local scope, you can use the global keyword.

The global keyword makes the variable global.

def myfunc():
  global x
  x = 300

myfunc()

print(x)

Also, use the global keyword if you want to make a change to a global variable inside a function.

x = 300

def myfunc():
  global x
  x = 200

myfunc()

print(x)