Dictionary Basics¶

Write code to create a dictionary grades that maps a student’s name to their assignment grade. grades has two entries in it:

Sam Reimer –> 84.3

Steve Bardeau –> 90.5
# replace this comment with your code ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertIs(type(grades), dict) self.assertEqual(len(grades), 2, 'dictionary must have 2 entries in it') self.assertAlmostEqual(grades['Sam Reimer'], 84.3) self.assertAlmostEqual(grades['Steve Bardeau'], 90.5) myTests().main()

You create a dictionary with { and }, and you put entries in it separating the key from the value with :.

grades = { 'Sam Reimer': 84.3, 'Steve Bardeau': 90.5 }

Write code to retrieve from dictionary grades the grade of ‘Colette Gonzales’. Store her grade in a variable colette_score. # replace this comment with your code ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertIs(type(grades), dict, 'grades is a dictionary') self.assertAlmostEqual(colette_score, 94.5, 'colette_score has the correct value') myTests().main()

Suppose you have a dictionary aDict. You can print the value with key key by doing print(aDict[key])

colette_score = grades['Colette Gonzales']

Write code to map floating point numbers to strings in a dictionary posOrNeg, initially containing these entries:

-3.14 –> ‘negative’

40.79 –> ‘positive’

0.01 –> ‘positive’
# replace this comment with your code ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertIs(type(posOrNeg), dict, 'posOrNeg is a dictionary') self.assertEqual(len(posOrNeg), 3, 'posOrNeg has 3 entries') self.assertEqual(posOrNeg[-3.14], 'negative') self.assertEqual(posOrNeg[40.79], 'positive') self.assertEqual(posOrNeg[0.01], 'positive') myTests().main()

You create a dictionary with { and }, and you put entries in it separating the key from the value with :.

posOrNeg = { -3.14: 'negative', 40.79: 'positive', 0.01: 'positive' }

Given a dictionary grades, write code to add an entry mapping John Fleenor to the grade 92.5. # replace this comment with your code ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertIs(type(grades), dict, 'grades is a dictionary') self.assertEqual(len(grades), 4, 'grade has 4 entries') self.assertAlmostEqual(grades['John Fleenor'], 92.5) myTests().main()

After a dictionary has been created you add entries using the syntax:

aDict[key] = value

grades['John Fleenor'] = 92.5

Given a dictionary grades containing a mapping of Sam Reimer to the grade 84.3, update the dictionary to change the grade to 94.3. # replace this comment with your code ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertIs(type(grades), dict, 'grades is a dictionary') self.assertEqual(len(grades), 3, 'grades has 3 entries') self.assertAlmostEqual(grades['Sam Reimer'], 94.3) myTests().main()

After a dictionary has been created you can update an entry using the syntax:

aDict[key] = value

(Just like creating a new entry.)

grades['Sam Reimer'] = 94.3

Given a dictionary grades containing a mapping of Sam Reimer to a floating point number, write code to add 1 to the grade. # replace this comment with your code ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertIs(type(grades), dict, 'grades is a dictionary') self.assertEqual(len(grades), 3, 'grades has 3 entries') self.assertAlmostEqual(grades['Sam Reimer'], 85.3) myTests().main()

Your code will have to access the value, add one to 1, and then update the entry. This can be done in one line of code.

grades['Sam Reimer'] = grades['Sam Reimer'] + 1