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Worksheet 5.41 Group Work: Functions with 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 5.41.1.

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.

Section 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

Subsection 5.41.1.1 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).

1.

What is the first thing that will be printed when the code below runs?

2.

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

Note 5.41.4.

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.

3.

What is the value of b when function test starts executing?

4.

Delete the last line of the function test above and run the code again. What value is returned from a function that doesn’t have a return keyword?

5.

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()

Subsection 5.41.1.2 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.

Subsection 5.41.1.3 String Indices

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

6.

What is the last thing that will be printed when the code below runs?

7.

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.

Note 5.41.10.

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)

Subsection 5.41.1.4 String Slices

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

8.

What is the last thing that will be printed when the code below runs?

9.

Run the code below to see what it prints.

Note 5.41.13.

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.

10.

Use the slice operator to return the first three characters from the variable dna?

11.

What built-in function tells you the number of characters in a string?

Subsection 5.41.1.5 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.

12.

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

13.

Run this code to see what it prints.

Note 5.41.18.

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

14.

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

15.

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

16.

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'

17.

What is the first thing that will be printed when the code below runs?

18.

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.

19.

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

Subsection 5.41.1.6 Logical Operators and Complex Conditionals

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

20.

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.

21.