Introduction

In our previous lesson, we discussed the many capabilities of functions with lists.

They can:

This last capability, mutating lists, is actually quite surprising! We aren’t able to do this with our previous data types, like strings.

For example, observe the following function:

    def emphasize(word: str):
        word += "!"

When we call this function on a string, we aren’t actually mutating the argument.

However, let’s do something similar for a list!

    def emphasize(word: list[str]):
        word.append("!")

This will actually mutate the list used as an argument in the function call!

For this challenge question, you are going to practice writing a function that mutates its input!

Part 0. Setup

Start by opening your workspace in Visual Studio. Right click on the “lessons” folder and select “add file”. Your file will be named mutate.py.

Set up your document by adding the docstring: """Mutating functions.""" and initializing the __author__ variable with your PID.

Write a function definition with the following expectations:

The function name is manual_append has a list[int] and an int as parameters.
The function should return nothing.
The function should mutate its input appending the int parameter to the end of the list[int] parameter.
Explicitly type variables, parameters, and return types.

Example usage:

>>> a: list[int] = [1,2,3]
>>> from lessons.mutate import manual_append
>>> manual_append(a, 2)
>>> print(a)
[1,2,3,2]

Write a function definition with the following expectations:

The function name is double and has a list[int] as a parameter.
The function should return nothing.
The function should mutate its input by multiplying every element in the list[int] parameter by 2
Explicitly type variables, parameters, and return types.

Example usage:

>>> a: list[int] = [1,2,3]
>>> from lessons.mutate import double
>>> double(a)
>>> print(a)
[2,4,6]

Hint: You will need to use a while loop to iterate over every element in the list.

Create a .zip file by running the following command in your terminal:

python -m tools.submission lessons/mutate.py

Then, drag and drop that .zip file into Gradescope!