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.

5.41.1. 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

5.41.2. Function Example

A function is a name for one or more lines of code. You first define a function using the def keyword and then execute it using function_name(arguments).

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.

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()
        

5.41.3. 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.

5.41.4. String Indices

You can get a character from a string at an index (position) using string[index].

Run the code below to see what it prints. Then fix it to pass the test shown below the code. 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 string[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.

5.41.5. String Slices

You can get a copy of part or all of a string using str_name[start:end].

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 index and include all the characters up to just before the end (the last character will be from index end - 1). If start is missing the default is 0 and if end is missing the default value is the length of the string.

5.41.6. Basic Conditionals and Tests

You can execute code only when a condition is true using if. You can execute one block of code when a condition is true (using if) or false (using else). You can even speicfy more than two outcomes as shown in the code below.

Run this code to see what it prints.

# 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 +.

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()

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'
        

Run this code to see what it prints. Then 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()

5.41.7. 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()

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()

If you worked in a group, you can copy the answers from this page to the other group members. Select the group members below and click the button to share the answers.

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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