03 Team Activity: Writing Functions

Instructions

Each lesson in CSE 111 contains a team activity that is designed to take about one hour to complete. You should prepare for all team activities by completing the preparation material and the individual checkpoint assignment before starting a team activity. The goal of the team activities is for students to work together and teach and learn from each other. As your team completes a team activity, instead of moving through it as quickly as you can, you should help everyone understand the concepts.

Face-to-Face Students

Face-to-face students will complete the team activities in their classroom during class time.

Online Students in a Semester Section

Online students in a semester section will arrange and participate in a one hour synchronous video meeting with your team for each team activity. As your team works through the assignment, be certain that each student can see the code that is being typed. When your team completes the video meeting, share the final Python file with everyone on your team.

Online Students in a Block Section

Students in a block section complete two lessons each week. This means that online students in a block section will complete two team activities each week. For one of these two activities, your team should arrange and participate in a one hour synchronous video meeting. For the other team activity, your team may meet in a synchronous video meeting or your team may collaborate, ask and answer questions, and share code in Microsoft Teams.

As your team works through a team assignment in a synchronous video meeting, be certain that each student can see the code that is being typed. When your team completes the video meeting, share the final Python file with everyone on your team.

Purpose

Boost your understanding of writing your own functions with parameters and then calling those functions with arguments.

Problem Statement

Health professionals who are helping a client achieve a healthy body weight, sometimes use two computed measures named body mass index and basal metabolic rate.

From the U.S. Centers for Disease Control and Prevention we read,

Body mass index (BMI) is a person’s weight in kilograms divided by the square of their height in meters. BMI can be used to screen for weight categories such as underweight, normal, overweight, and obese that may lead to health problems. However, BMI is not diagnostic of the body fatness or health of an individual.

The formula for computing BMI is

bmi =

10,000 weight

height²

where weight is in kilograms and height is in centimeters.

Basal metabolic rate (BMR) is the minimum number of calories required daily to keep your body functioning at rest. BMR is different for women and men and changes with age. The revised Harris-Benedict formulas for computing BMR are

(women) bmr = 447.593 + 9.247 weight + 3.098 height − 4.330 age

(men) bmr = 88.362 + 13.397 weight + 4.799 height − 5.677 age

where weight is in kilograms and height is in centimeters.

Assignment

Work as a team to write a Python program named fitness.py that does the following:

Asks the user to enter four values:
1. gender
2. birthdate in this format: YYYY-MM-DD
3. weight in U.S. pounds
4. height in U.S. inches
Converts the weight from pounds to kilograms (1 lb = 0.45359237 kg).
Converts inches to centimeters (1 in = 2.54 cm).
Calculates age, BMI, and BMR.
Prints age, weight in kg, height in cm, BMI, and BMR.

Helpful Documentation

The preparation content for the previous lesson explains how to call functions.
The prepare content for this lesson explains how to write functions.
The official Python reference describes the built-in round function.

Steps

Copy and paste the following code into a new program named fitness.py. Use the pasted code as a design as you write your program. Write code for each of the functions except compute_age. The compute_age function is complete and correct, and you should not change it.

# Import datetime so that it can be
# used to compute a person's age.
from datetime import datetime


def main():
    # Get the user's gender, birthdate, height, and weight.

    # Call the compute_age, kg_from_lb, cm_from_in,
    # body_mass_index, and basal_metabolic_rate functions
    # as needed.

    # Print the results for the user to see.
    pass


def compute_age(birth_str):
    """Compute and return a person's age in years.
    Parameter birth_str: a person's birthdate stored
        as a string in this format: YYYY-MM-DD
    Return: a person's age in years.
    """
    # Convert a person's birthdate from a string
    # to a date object.
    birthdate = datetime.strptime(birth_str, "%Y-%m-%d")
    today = datetime.now()

    # Compute the difference between today and the
    # person's birthdate in years.
    years = today.year - birthdate.year

    # If necessary, subtract one from the difference.
    if birthdate.month > today.month or \
        (birthdate.month == today.month and \
            birthdate.day > today.day):
        years -= 1

    return years


def kg_from_lb(pounds):
    """Convert a mass in pounds to kilograms.
    Parameter pounds: a mass in U.S. pounds.
    Return: the mass in kilograms.
    """
    return


def cm_from_in(inches):
    """Convert a length in inches to centimeters.
    Parameter inches: a length in inches.
    Return: the length in centimeters.
    """
    return


def body_mass_index(weight, height):
    """Compute and return a person's body mass index.
    Parameters
        weight: a person's weight in kilograms.
        height: a person's height in centimeters.
    Return: a person's body mass index.
    """
    return


def basal_metabolic_rate(gender, weight, height, age):
    """Compute and return a person's basal metabolic rate.
    Parameters
        weight: a person's weight in kilograms.
        height: a person's height in centimeters.
        age: a person's age in years.
    Return: a person's basal metabolic rate in kcals per day.
    """
    return


# Call the main function so that
# this program will start executing.

Core Requirements

Your program contains complete and correct functions named compute_age, kg_from_lb, and cm_from_in.
Your program contains complete and correct functions named body_mass_index and basal_metabolic_rate. To be correct, the basal_metabolic_rate function must compute BMR differently for males and females.
Your program contains a function named main which gets four values from the user, calls the other functions, and prints the results for the user to see.

Stretch Challenges

If your team finishes the core requirements in less than an hour, complete one or more of these stretch challenges. Note that the stretch challenges are optional.

Modify your program to print the height values in meters instead of centimeters.
Modify your program to allow the user to enter weight in British stones and add a function named kg_from_stone.
Modify your program to allow the user to enter height as U.S. feet and inches.
Add something or change something in your program that you think would make your program better, easier for the user, more elegant, or more fun. Be creative.

Testing Procedure

Verify that your program works correctly by following each step in this testing procedure:

Run your program and enter the inputs shown below. Ensure that your program’s output is similar* to the output below.

> python fitness.py
Please enter your gender (M or F): F
Enter your birthdate (YYYY-MM-DD): 2001-03-21
Enter your weight in U.S. pounds: 125
Enter your height in U.S. inches: 54
Age (years): 19
Weight (kg): 56.70
Height (cm): 137.2
Body mass index: 30.1
Basal metabolic rate (kcal/day): 1315

> python fitness.py
Please enter your gender (M or F): M
Enter your birthdate (YYYY-MM-DD): 2003-11-26
Enter your weight in U.S. pounds: 145
Enter your height in U.S. inches: 58
Age (years): 17
Weight (kg): 65.77
Height (cm): 147.3
Body mass index: 30.3
Basal metabolic rate (kcal/day): 1580

Note that the output of your program will not be the same for the age and BMR values because a computer executed these sample runs before you executed your program. Therefore, when you run your program, the people will be older than they were when the computer completed these sample runs.

Sample Solution

Please work diligently with your team for the one hour meeting. After the meeting is over, please compare your solution to the sample solution. Please do not look at the sample solution until you have either finished the program or diligently worked for at least one hour. At the end of the hour, if you are still struggling to complete the assignment, you may use the sample solution to help you finish.

Call Graph

The following call graph shows the function calls and returns in the sample solution for this assignment. From this call graph we see the following function calls:

The computer starts executing the sample program by calling the main function.
While executing the main function, the computer calls the input and float functions.
While still executing the main function, the computer calls the compute_age, kg_from_lb, cm_from_in, body_mass_index, and basal_metabolic_rate functions.
Finally, while still executing the main function, the computer calls the print function.

A function call graph for this assignment

Ponder

After you finish this assignment, congratulate yourself because you wrote a Python program with six user-defined functions named main, compute_age, kg_from_lb, cm_from_in, body_mass_index, and basal_metabolic_rate. You also wrote code to call those six functions. Why is it important that you know how to write your own functions?

Submission

When you have finished the activity, please report your progress via the associated I‑Learn quiz. When asked about which of the requirements you completed, feel free to include any work done during the team meeting or after the meeting, including work done with the help of the sample solution, if necessary. In short, report on what you were able to accomplish, regardless of when you completed it or if you needed help from the sample solution.