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5.41. Group Work: Functions, Strings, and Conditionals

It is best to use a POGIL approach with the following. In POGIL students work in groups on activities and each member has an assigned role. For more information see https://cspogil.org/Home.

Note

If you work in a group, have only one member of the group fill in the answers on this page. You will be able to share your answers with the group at the bottom of the page.

Learning Objectives

Students will know and be able to do the following.

Content Objectives:

• Learn how to display a value in Python using print.

• Match terms for functions to their definitiions.

• Recognize common symbols (:, #), operators (+, -, /), and keywords (def, return) in Python.

• Recognize strings.

• Use string indices.

• Understand how slice works for both positive and negative indices.

• Use input and convert between strings and numbers.

• Recognize common string methods.

• 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:

• Learn how to properly indent the body of a function

• Predict the output from code.

• Modify code to produce the correct output.

• Create good test data for functions with conditionals

• Modify code to use complex conditionals

5.41.1. Function Example

Q-1: What is the first thing that will be printed when the code below runs?

Run the Python code below and then answer the following questions.

Run the code below to see what it prints and then use it to answer the following questions.

# function definition def test(a, b = 2): print("Welcome") print("Learn the power of functions!") print(a + b) print(a - b) print(a * b) print(a / b) print(a // b) a = 5 % 2 return a # function definition def main(): print("Hello!") # function call print(test(3)) # function call main()

Note

You do not declare the type of a variable in Python. Python requires that all statements that are part of the body of a function must be indented. Use four spaces to indent.

Q-3: What is the value of b when function test starts executing?

Delete the last line of the test function above and run the code again.

Q-4: What value is returned from a function that doesn’t have a return keyword?

Drag the blocks from the left and put them in the correct order on the right to define a function print_greeting that asks for your name and prints “Hello Name”. Then define a main function that calls print_greeting. Be sure to also call the main function. Note that you will have to indent the lines that are in the body of each function. Click the Check button to check your solution.

        def print_greeting():
---
def print_greeting() #paired
---
    name = input("What is your name?")
---
    print("Hello " + name)
---
def main():
---
Def main(): #paired
---
    print_greeting()
---
    print_greeting #paired
---
main()
        

5.41.2. String Definition

A string is a sequence of characters enclosed in quotes. In Python you can use pairs of single or double quotes to enclose a string like in "hello" or 'hello'. This is especially useful when a string includes a single quote "they're". You can even use tripe quotes when a string covers more than one line.

5.41.3. String Indices

Q-6: What is the last thing that will be printed when the code below runs?

Run the code below to see what it prints. Then fix it to pass the given test. It should return a string with the first character of the first name and first character of the last name.

# function definition def get_initials(first, last): return first[0] + last[-1] # function definition def main(): print(type("Hello")) print(type('Class')) print(type(42)) print(get_initials("J'Quan",'Alik')) # function call main() from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(get_initials("J'Quan",'Alik'),"JA",'''get_initials("J'Quan",'Alik')''') myTests().main()

Note

Use [index] to get a character from a string. The first character in a string is at index 0 and the last is at the length of the string minus 1 (also know as index -1 in Python).

Fix the function get_initials above to return a string with the first letter of the first name followed by the first letter of the last name.

5.41.4. String Slices

Q-8: What is the last thing that will be printed when the code below runs?

Run the code below to see what it prints.

# function definition def get_short_name(first, last): print(len(first)) print(len(last)) return first[:2] + last[-2:] # function definition def main(): print(get_short_name('Simona',"Jacobs")) # function call main()

Note

Use the slice [start:end] operator to get a slice (substring) from a string. It will return a new string starting at the start and including all the characters up to just before the end (end - 1). If start is missing the default is 0 and if end is missing the default value is the length of the string.

Q-10: Use the slice operator to return the first three characters from the variable dna?

5.41.5. Basic Conditionals and Tests

Q-11: What is the first thing (first line of text) that will be printed when the code below runs?

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()

Q-13: What keyword is used in a conditional statement when you want three of more possible outcomes?

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! The temp is " + str(temp) elif temp < 70: return "Wear a coat. The temp is " + str(temp) elif temp < 80: return "Feels great! The temp is " + str(temp) else: return "Too hot to handle! The temp is " + str(temp) # function definition def main(): print(get_temp_desc(20)) print(get_temp_desc(85)) # function call main()

Note

You must first convert a number to a string using str(nun) if you want to add it to a string using +.

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'
        

Q-16: What is the first thing that will be printed when the code below runs?

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()

Q-18: How many test cases do you need to check that the code above works as intended?

5.41.6. Logical Operators and Complex Conditionals

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

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()

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The Submit Group button will submit the answer for each each question on this page for each member of your group. It also logs you as the official group submitter.

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