Learn

We just witnessed that we can access names from the enclosing scope with nested functions, but we cannot modify them. Python does however provide a way for us to modify names in the enclosing scope, by using the nonlocal statement.

Given the following enclosing and nested function, there is a variable defined in the enclosing scope, which is not modifiable from within the nested function.

def enclosing_function():
  var = "value"

  def nested_function():
    var = "new_value"

  nested_function()

  print(var)

enclosing_function()

The output would be:

value

as the value of var was not modified by the nested function. After using the nonlocal statement, the variable is now modifiable from the local scope.

def enclosing_function():
  var = "value"

  def nested_function():
    nonlocal var
    var = "new_value"

  nested_function()
  print(var)

enclosing_function()

The output would now be:

new_value

Let’s practice modifying variables in a nested context in our painting application for Jiho!

Instructions

The users of our applications have requested that we add a way of calculating the amount of paint needed for multiple rooms. To accomplish this the function calc_paint_amount() now accepts a single parameter wall_measurements which should be a list of tuples containing the width and height of each wall.

The nested function calc_square_feet() has been added to iterate through the list and add up the square footage. This function is then called within calc_paint_amount().

Run the code and notice the UnboundLocalError regarding the variable square_feet. Move to the next task to fix this.

Since we need to modify square_feet in an enclosing scope, make sure to mark the variable as nonlocal in the appropriate place.

Sign up to start coding

By signing up for Codecademy, you agree to Codecademy's Terms of Service & Privacy Policy.

Or sign up using:

Already have an account?