SB Exercises

Exercises 20.9 Exercises

1.
A function named reverse takes a string argument, reverses it, and returns the result:
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def reverse(astring): """Returns the reverse of `astring`"""

Complete the assert statements in the ActiveCode editor below to create a unit test for reverse. Your asserts should check that reverse works properly for the following test cases (“Input” refers to the value passed as a parameter, and “Expected Output” is the result returned from reverse):
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Input Expected Output -------- --------------- Test Case 1: 'abc' 'cba' Test Case 2: 'b' 'b' Test Case 3: '' ''

def test_reverse(): # Complete the assert statements below assert ________________ assert ________________ assert ________________ ==== from unittest.gui import TestCaseGui testABC = False testB = False testEmpty = False def reverse(astring): """Returns the reverse of `astring`""" global testABC, testB, testEmpty if astring == 'abc': testABC = True elif astring == 'b': testB = True elif astring == '': testEmpty = True l = list(astring) l.reverse() return ''.join(l) class myTests(TestCaseGui): def testOne(self): test_reverse() code = self.getEditorText().replace(' ','').replace('"', '').replace("'", '') self.assertTrue(testABC and '==cba' in code, "Assert tested 'abc'") self.assertTrue(testB and '==b' in code, "Assert tested 'b'") self.assertTrue(testEmpty and '==\n' in code, "Assert tested ''") myTests().main()
Hint.

If you’re not sure how to get started with this one, review Section 20.5.
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Solution.

assert reverse('abc') == 'cba' assert reverse('b') == 'b' assert reverse('') == ''

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2.

A function named stripletters takes a string argument, removes all letters from it, and displays the result (see below). However, this function is not testable.
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Modify the function so that it can be tested with the assert statements that follow.
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def stripletters(msg): result = '' for ch in msg: if not ch.isalpha(): result += ch print(result) assert stripletters('ab12c') == '12' assert stripletters('12') == '12' ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(stripletters('ab12c'), '12', "stripletters('ab12c') == '12'") self.assertEqual(stripletters('12'), '12', "stripletters('12') == '12'") myTests().main()
Hint.

Review Section 20.4.
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Solution.

def stripletters(msg): result = '' for ch in msg: if not ch.isalpha(): result += ch return result

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Exercises 20.9 Exercises

1.

2.