CS170: Programming for the World Around Us - Functions with Python

Activity Goals

The goals of this activity are:
  1. To be able to call methods in various configurations (parameters, return values)
  2. To use functions with return values

Supplemental Reading

Feel free to visit these resources for supplemental background reading material.

The Activity

Directions

Consider the activity models and answer the questions provided. First reflect on these questions on your own briefly, before discussing and comparing your thoughts with your group. Appoint one member of your group to discuss your findings with the class, and the rest of the group should help that member prepare their response. Answer each question individually from the activity, and compare with your group to prepare for our whole-class discussion. After class, think about the questions in the reflective prompt and respond to those individually in your notebook. Report out on areas of disagreement or items for which you and your group identified alternative approaches. Write down and report out questions you encountered along the way for group discussion.

Model 1: Writing and Invoking Functions to Re-Use Code Logic

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import math
 
# Return the area of a circle, given its radius
# param radius: the radius of the circle
# Precondition: radius >= 0
# return: the area of the circle in square units of the radius 
def circleArea(radius):
    area = math.pi * (radius ** 2)
    return area
     
def triangleArea(base, height):      
    area = (base * height) / 2
    return area
     
def main():
    r = 10
    area = circleArea(r)
    print("The area of the circle is {0:.,2f}".format(area))
     
if __name__ == "__main__":
    main()

Questions

  1. Try running the sample program above.
  2. What does return mean in the circleArea function above?
  3. Notice that functions have data types before their function names, just like variables do. What is the return type of circleArea()?
  4. Modify the program to write an additional function circleDiameter() that computes the diameter (2×π×r) given the radius of the circle. Call that function from main() and print the value.
  5. Modify the program to write and call triangleArea() from main() and then print the area of a triangle whose dimensions you choose.
  6. Write an if statement to tell if room temperature is between 70 and 74 degrees (you can print out a message saying whether or not it is in this range). Then, migrate this to a function that accepts the temperature as a parameter, and call this function at least twice from main(). Next, add a second parameter to this function to represent the humidity, and display a separate message indicating whether it is within a range of 30 and 50 percent. Finally, modify your function to return a boolean if both conditions are met. How might you use this logic to control a thermostat device?
  7. Write comments for the triangleArea() function similar to the circleArea function.

Reflective Journal Prompt

  1. Notice the comments above the circleArea function. What do you think a precondition means?
  2. Write comments for the triangleArea function in a similar spirit to those of the circleArea function.

Submission

I encourage you to submit your answers to the questions (and ask your own questions!) using the Class Activity Questions discussion board. You may also respond to questions or comments made by others, or ask follow-up questions there. Answer any reflective prompt questions in the Reflective Journal section of your OneNote Classroom personal section. You can find the link to the class notebook on the syllabus.