COS 100: Introduction to Programming

Interim 2022

Lab 11: List mutation

In this lab, we will write several functions that mutate (change) the given list. A function that acts by mutating its input often has the words "in place" in the specification. Look for those words below.

1. Write a function increment that takes a list of numbers and increases every number by 1 in place. The function should not return anything (well, it returns None automatically), but rather, mutates the given list.

   For example, after you are done writing the function increment, the following code

   numbers = [2, 7., 1, 8]
   increment(numbers)
   print(numbers)
   

   should print

   [3, 8.0, 2, 9]
   

2. Write a function swap that takes a list and two numbers i and j and swaps the ith and jth entry of the list in place.

   yoda = ["mutation", "easy", "is", "!"]
   swap(yoda, 1, 2)
   print(yoda)
   

   ['mutation', 'is', 'easy', '!']
   

3. Write a function reverse that takes a list and reverses it in place.

   mixed = [2, "word", 3, "tofu"]
   reverse(mixed)
   print(mixed)
   

   ['tofu', 3, 'word', 2]
   

   Make sure your function works for lists of both even and odd lengths.
4. (Bonus) Write a function sort that takes a list of numbers and sorts it from smallest to largest in place.

   numbers = [2, 7., 1, 8]
   sort(numbers)
   print(numbers)
   

   [1, 2, 7.0, 8]