Lab 6: Functions and Function Composition

CSCI 141
Lab 6: Functions and Function Composition
Introduction
By this time in the quarter you’ve seen functions in lecture, in lab, and from here on they will
be required in the coding portions of the homework assignments, including A4 which is due this
week.
In this lab, you’ll write a program that calculates the total square footage in a home. Imagine
you are working for a construction company that builds homes with only square or rectangular
rooms. The houses vary in size, with as little as 1 room and up to 100s. Your task is to
write a program that will prompt the user to input the number of rooms and their
dimensions, and which then calculates the total square footage of the home. Two
invocations of such a program are shown below.
Figure 1: Two sample invocations
The figure on the left is the program running where a user specifies a house with 3 rooms – a
square room and two rectangle rooms. The image on the right is the calculation for a house
with 4 rooms – three square rooms and a rectangular room.
You’ll create such a program from scratch. You’ll be asked to follow good coding conventions
– if you find yourself typing similar code over and over again, create a function for performing
that repeated task (as was shown in lecture).
Look at the above program invocations, and notice the following:
• To calculate the size of a square room, you need only the dimension of one of the walls
• To calculate the size of a rectangular room, you need both dimensions, the width and
length
• There are repeated print statements that are very similar, but not identical. However,
they all begin with “What is the”, and end with a question mark.
From these observations, your supervisor (boss) has decided that your program can have ONLY
3 functions:
1. room_square_feet, which takes a single argument to designate whether the room is a
square or rectangular room. If the room is a square room, the function room_square_feet
1
invokes the prompt_user function once to retrieve the single dimension needed to calculate
the size of the room. If the room is a rectangular room, the function room_square_feet
invokes the prompt_user function twice to retrieve the two dimensions needed to calculate
the room’s size. The function room_square_feet returns the square footage of a room.
2. main, which prompts the user for the count of rooms and calls room_square_feet for
each room, using the accumulator pattern (refer to Section 6.4 of the textbook) to keep
a running total of the square footage of the house.
3. prompt_user, which receives two arguments and returns one value. The first parameter,
of type str, is the text of the question that the user is prompted. In the examples above,
“length of the room” and “width of the room” and “shape of room 1, square or rectangle”
would be the three Strings that are provided as input on three separate occasions to the
function prompt_user. The second argument designates the return type of the function.
Hint: use type conversion function(s) to convert the user’s input into the appropriate
type of data to be returned. A diagram showing two example usages of the prompt_user
function for two sample inputs is included below.
prompt_user “number of rooms”
“integer”
Prompt user : What is
the number of rooms?
User inputs : “4”
inputs outputs
4
(type int)
prompt_user “shape of room 2”
“string”
Prompt user : What is
the shape of room 2?
User inputs :
“rectangle”
inputs outputs
“rectangle”
(type str) 1 Setup
Create a lab6 folder and in it create a Python file called squarefootage.py.
2 Example Program Flow
The steps below illustrate an example of the program’s behavior when prompting for the information and calculating the square footage of a single room. Recall that your main program
will do this once for each room in the house. Notice that main uses prompt_user twice, then
calls room_square_feet, which itself calls prompt_user once or twice depending on the shape
of the room.
2
Step 1: prompt_user is invoked with first and second arguments “shape of room 1” and “string”
both of type string.
Step 2: prompt_user prompts the user with the question “What is the shape of room 1?”
Step 3: The user responds to the prompt and types “square”
Step 4: prompt_user returns the string “square”, which is then passed to the function room_square_feet
Step 5: The function room_square_feet calls prompt_user with two arguments, “side length of
square room” and “integer”
Step 6: The function prompt_user prompts the user with the question “What is the side length
of square room”
Step 7: The user responds to the prompt and types “12”
Step 8: The function prompt_user returns the integer 12, which is saved in a variable in the
function room_square_feet
Step 9: The function room_square_feet calculates the size of the room (12 ∗ 12) and returns the
integer 144.
3 Game Plan and Guidelines
• All three functions are fairly simple, taken by themselves. You should be able to write
each one in less than about 10 lines of code.
• Start by writing a header and specification for the prompt_user function based on the
description above. Then implement the function and test it using the interactive shell.
Test it for both integer and string output types.
• Write a header and specification for room_square_feet. Implement it, using your alreadytested prompt_user function, and test its functionality in the interactive shell.
• Write the main function, noting that it takes no arguments and has no return value; when
the total square footage is calculated, print the total.
• Finally, at the bottom of your program, call your main function in a main guard so that
running the program calls the main function:
if __name__ == "__main__":
main()
• As usual, you are not required to check for and handle input from badly behaved users:
you may assume the user enters numbers when they’re supposed to, and that they enter
either square or rectangle for the shape of each room.
• We test your programs with automated scripts, so the prompts must be made in exactly
the order shown in the sample outputs to receive full credit. The text of the prompts
does not need to match exactly, but the order must match.
3
Submission
Submit squarefootage.py via Canvas.
Rubric
Your file is called squarefootage.py and has a comment specifying author, date,
and purpose at the top.
1 points
Your program uses good, descriptive variable names 2
main, room_square_feet, and prompt_user have headers and docstrings consistent with the description in the lab handout
6
Each function is at most 10 lines of code (not counting comments) 6
prompt_user prompts the user and returns the correct type 4
room_square_feet uses prompt_user to prompt for the dimensions 2
main uses prompt_user to specify how many rooms 2
main calls prompt_user to prompt for shape of the room 2
main calls room_square_feet for each room and the return value is added to an
accumulator variable
2
main function prints correct final square footage 3
Total 30 points
4