List Basics — Runestone Interactive Overview

Write code to create a list called greetings containing the string ‘hello’ and the string ‘nihao’. # replace this comment with your code ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(greetings, ['hello', 'nihao']) myTests().main()

Use [ and ] and separate the strings with commas.

greetings = ['hello', 'nihao']

Write a statement to create a variable emptyList referring to an empty list. # replace this comment with your code ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(emptyList, []) myTests().main()

You can create an empty list by using [ and ] with nothing in between.

emptyList = []

Write code to print the element at index 2 from a previously-defined list groceries. # replace this comment with your code ====

Call print(), accessing groceries inside it.

print(groceries[2])

Write code to print the 2nd-to-last element of previously-defined list groceries. # replace this comment with your code ====

Use -2 to access the 2nd-to-last element.

print(groceries[-2])

Write code to create a list containing 3 elements, your name, your age, your eye color, where your name and eye color are strings, and your age is a number. # replace this comment with your code ====

Lists can contain elements of any type.

myInfo = ['Victor Norman', 53, 'hazel']

Write a line of code to replace the element at index 1 of a previously-defined list groceries with the string ‘chocolate milk’. # replace this comment with your code ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(groceries[1], 'chocolate milk') self.assertEqual(len(groceries), 5) myTests().main()

To replace an element in a list, access that element on the left-hand-side of an assignment statement.

groceries[1] = 'chocolate milk'

Write code that removes the first item (at index 0) from a list groceries and adds that item back at the end of the list. # replace this comment with your code ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(len(groceries), 5) self.assertEqual(groceries[-1], 'milk') self.assertEqual(groceries[-2], 'bread') self.assertEqual(groceries[0], 'eggs') myTests().main()

Use two lines of code. Use pop() in the first line, and append() in the second.

item = groceries.pop(0) groceries.append(item)

Write code to remove the last item of the list groceries and insert it in the middle of the list. Assume the list has an odd number of elements before removing the last item (and, thus, an even number of elements after removing the last item). (Hint: use integer division //.) # replace this comment with your code ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(len(groceries), 5) self.assertEqual(groceries[0], 'milk') self.assertEqual(groceries[1], 'eggs') self.assertEqual(groceries[2], 'bread') self.assertEqual(groceries[3], 'chocolate!') self.assertEqual(groceries[4], 'Doritos!') myTests().main()

Use multiple lines of code. First, pop() the last item off and store it in a variable. Then, get the length of the list. Then insert the item back into the list in the middle.

item = groceries.pop() listlen = len(groceries) groceries.insert(listlen // 2, item)

Write code to swap the first and last items in the list groceries. # replace this comment with your code ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(len(groceries), 5) self.assertEqual(groceries[0], 'bread') self.assertEqual(groceries[1], 'eggs') self.assertEqual(groceries[2], 'chocolate!') self.assertEqual(groceries[3], 'Doritos!') self.assertEqual(groceries[4], 'milk') myTests().main()

Do this in 4 steps: remove the last item and store in a variable. Remove the first item and store in a variable. Then, in two lines of code, add the items back to the list, using insert() and append().

firstitem = groceries.pop(0) lastitem = groceries.pop() groceries.insert(0, lastitem) groceries.append(firstitem)

Write code to create a new list allitems that is the concatenation of list groceries and list clothes. # replace this comment with your code ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(len(allitems), 7) self.assertEqual(allitems[0], 'milk') self.assertEqual(groceries[4], 'bread') self.assertEqual(groceries[5], 'socks') self.assertEqual(groceries[6], 'leggings') myTests().main()

You can concatenate lists using +.

allitems = groceries + clothes

Given a list scores, write code to store the average in a variable called average_score. Then, print average_score. # replace this comment with your code ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(average_score, sum(scores) / len(scores)) myTests().main()

Use sum(scores) and len(scores) in your computation.

average_score = sum(scores) / len(scores) print(average_score)

List Basics¶