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4.0 Python: Scope

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

4.1 Local Scope​

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

4.1.1 Example​

A variable created inside a function is available inside that function:

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

myfunc()

4.1.2 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:

4.1.3 Example​

The local variable can be accessed from a function within the function:

def myfunc():
    x = 300

    def myinnerfunc():
        print(x)
    myinnerfunc()

myfunc()

4.2 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.

4.2.1 Example​

A variable created outside of a function is global and can be used by anyone:

x = 300

def myfunc():
    print(x)

myfunc()

print(x)

4.2.2 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):

4.2.3 Example​

The function will print the local x, and then the code will print the global x:

x = 300

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

myfunc()

print(x)

4.3 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.

4.3.1 Example​

If you use the global keyword, the variable belongs to the global scope:

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.

4.3.2 Example​

To change the value of a global variable inside a function, refer to the variable by using the global keyword:

x = 300

def myfunc():
  global x
  x = 200

myfunc()

print(x)

4.4 Nonlocal Keyword​

The nonlocal keyword is used to work with variables inside nested functions.

The nonlocal keyword makes the variable belong to the outer function.

4.4.1 Example​

If you use the nonlocal keyword, the variable will belong to the outer function:

def myfunc1():
  x = "Jane"
  def myfunc2():
    nonlocal x
    x = "hello"
  myfunc2()
  return x

print(myfunc1())