5.25. Group Work: Functions and Conditionals

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Note

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Learning Objectives

Students will know and be able to do the following.

Content Objectives:

• Recognize the keywords used in conditionals in Python (if, elif, else).

• Predict the output from simple and complex conditionals.

• Recognize the keywords used in complex conditionals (and, or, not).

Process Objectives:

• Create good test data for functions with conditionals

• Modify code to use complex conditionals

5.25.1. Basic Conditionals and Tests

Run this code to see what it prints.

# function definition def get_temp_desc(temp): if temp < 32: return "Baby, its cold outside!" elif temp < 70: return "Wear a coat" elif temp < 80: return "Feels great!" else: return "Too hot to handle!" # function definition def main(): print(get_temp_desc(20)) print(get_temp_desc(85)) # function call main()

Modify the code in the main method below to test all possible return values from get_temp_desc.

# function definition def get_temp_desc(temp): if temp < 32: return "Baby, its cold outside!" elif temp < 70: return "Wear a coat" elif temp < 80: return "Feels great!" else: return "Too hot to handle!" # function definition def main(): print(get_temp_desc(20)) print(get_temp_desc(85)) # function call main()

Put the blocks in order to define the function check_guess which will return 'too low' if the guess is less than the passed target, 'correct' if they are equal, and 'too high' if the guess is greater than the passed target. For example, check_guess(5,7) returns 'too low', check_guess(7,7) returns 'correct', and check_guess(9,7) returns 'too high'. There are three extra blocks that are not needed in a correct solution.

        def check_guess(guess, target):
---
    if guess < target:
---
    if guess < target #paired
---
        return 'too low'
---
        return "too low' #paired
---
    elif guess == target:
---
    elif guess = target: #paired
---
        return 'correct'
---
    else:
---
        return 'too high'
        

Finish the function last_half(str) which returns the last half of the characters from the passed string str. If str has less than 2 characters then return the empty string "". For example, last_half("a") returns "", last_half("coal") returns "al", and last_half("bye") returns ye.

def last_half(str): ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(last_half('a'), '', "last_half('a')") self.assertEqual(last_half('coal'), 'al', "last_half('coal')") self.assertEqual(last_half('bye'), 'ye', "last_half('bye')") self.assertEqual(last_half('abcd'), 'cd', "last_half('abcd')") self.assertEqual(last_half('12345'), '345', "last_half('12345')") self.assertEqual(last_half('123456'), '456', "last_half('123456')") self.assertEqual(last_half('ab'), 'b', "last_half('ab')") self.assertEqual(last_half(''), '', "last_half('')") myTests().main()

Run this code to see what it prints. The modify it to work correctly. Next, add code to the main function to test each possible letter grade. It should return A if the score is greater than or equal 90, B if greater than or equal 80, C if greater than or equal 70, D if greater than or equal 60, and otherwise E.

# function definition def get_grade(score): grade = None if score > 90: grade = 'A' if score > 80: grade = 'B' if score > 70: grade = 'C' if score > 60: grade = 'D' else: grade = 'E' return grade def main(): print(get_grade(95)) main()

5.25.2. Logical Operators and Complex Conditionals

The logical operators in Python are and, or, and not. These can be used to create complex conditionals.

Q-12: Which of the following tests if x is both greater than 10 and less than or equal to 20?

• x > 10 and < 20

• You have to check that x is greater than 10 and x is less than or equal 20. You must repeat the x.

• x > 10 && x <= 20

• Python uses the keyword and, not &&

• x > 10 and x <= 20

• This will be true when x is greater than 10 and less than or equal 20

• x > 10 && x < 20

• Python uses the keyword and, not && and this will be true when x is greater than 10 and less than 20

Q-13: Which of the following returns true if have_ride is true or can_walk is true?

• have_ride and can_walk

• Both must be true for this to be true

• have_ride or can_walk

• This will return true when one of these is true

• have_ride || can_walk

• Python uses the keyword or, not ||

• have_ride OR can_walk

• Python keywords are all lowercase

Q-14: Which of the following returns true if is_raining is false? Pick all that are correct.

• ! is_raining

• Python does not use the ! symbol for not

• not is_raining

• This will return True when is_raining is false.

• is_raining

• If is_raining is false this will return False.

• is_raining == False

• This will return True when is_raining is False.

Modify this code to use a complex conditional instead. It should still pass all tests. It should only take four lines of code or less.

# function definition def either6(a,b): if a == 6: return True if b == 6: return True return False ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(either6(5,2),False,"either6(5,2)") self.assertEqual(either6(6,3),True, "either6(6,3)") self.assertEqual(either6(3,6),True, "either6(3,6)") self.assertEqual(either6(3,-6),False, "either6(3,6)") myTests().main()

Modify this code to use a complex conditional instead. It should still pass all tests. It should only take four lines of code or less.

# function definition def test(a): if a > 0: if a <= 10: return True return False ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(test(5),True,"test(5)") self.assertEqual(test(0),False,"test(0)") self.assertEqual(test(1),True,"test(1)") self.assertEqual(test(-5),False,"test(-5)") self.assertEqual(test(11),False,"test(11)") self.assertEqual(test(10),True,"test(10)") self.assertEqual(test(9),True,"test(9)") myTests().main()

Drag the blocks from the left and put them in the correct order on the right to define a function squirrel_play that takes a temp (the temperature) and Boolean is_summer that indicates if it is summer or not and returns True if it is summer and the temperature is between 60 and 100 (inclusive). It also returns True if it isn’t summer and the temperature is between 60 and 90 (inclusive). Otherwise, it returns False.

        def squirrel_play(temp, is_summer):
---
    if is_summer and temp >= 60 and temp <= 100:
---
        return True
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        return true #paired
---
    elif not is_summer and temp >= 60 and temp <= 90:
---
    else if not is_summer and temp >= 60 and temp <= 90: #paired
---
        return True
---
    else:
---
    else #paired
---
        return False
---
        return false #paired
        

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