4.1: User Input

Goals:

By the end of this lesson, I will be able to:

1. Identify the importance of input in programs
2. Create and run programs that include user interaction
3. Store and modify user inputs
4. Utilize user input to make decisions in a program
5. Allow user input to change program flow during flight

Steps to Success:

1. Input
2. Dizzy Drone Activity
3. Creating a Menu
4. Make Your Own Menu
5. Resetting and User Input
6. Making Decisions
7. Final Code
8. Challenge: Custom Polygon

Up to this point, you cannot interact with the code or change its behavior while it is running. The code that you write will run exactly the same way each time. In this lesson, you will learn how to affect the output of the code using the input() function. The input() function is a way for the user to assign variables while the program is running.

The input() function is actually pretty simple, it looks like this:

stored_value = input("Enter a value to save")

What you will notice is that we always save the input to a variable. The only parameter it has is a string that it uses to prompt the user to enter a question. To see this in action, watch the video below and follow along:

Before we get started with the dizzy drone activity, we need to understand a little more about how the input() function works and what type of value it is actually giving us.

To recap:

• The input function gives us a string.
• If we want to change the string to an integer, we use the int(value) function
• We can tell what data type a variable is by using the type(value) function
• To make our program more user-friendly, we need to make sure the prompt asks for the correct types of information

Now that we have an understanding of how to use the input() function, let’s try an example.

We want to write a program that tells the drone to spin around a set number of times. The number of times it will spin around is based on user input from the input() function.

The code should look like:

import time

from codrone_edu.drone import *
drone = Drone()
drone.pair()

# Ask user how many times to spin around
num_spins = int(input("How many times should the drone spin:"))

drone.takeoff()
drone.hover(1)

drone.set_yaw(50)
i = 0
while i < num_spins: # start counting at 0
    drone.move(5)
    i += 1

drone.land()

One of the best ways to understand the input() function in action is by creating a menu of flight movements. A menu is a list of options to select from. You have probably selected a meal before from a restaurant menu or selected a character from a video game screen. Menus allow the user to select a particular outcome. In programming, this means that your program can now handle lots of different cases.

In this lesson, you will be writing a program that will ask a user to select a flight sequence and then send the right commands to the drone.

Ready to make your own? Import the “time” library. Next, set up a while loop so that while true, the menu will be printed. 

Inside the while loop, include print commands for a “Menu” and then options for different maneuvers that you would like your CoDrone EDU to do. This can be anything, but you should have an idea of how to program each maneuver you include! Make sure one of those options is “Quit”, which will end the while loop.

Your menu should look something like this:

from codrone_edu.drone import *

drone = Drone()

drone.pair()


while True:

    print("Menu: ")

    print("1. Spin Around n"

        "2. Fly in a triangle n"

        "3. Fly in a square n"

        "4. Sway n"

        "5. Quit n")

Wondering what the  n is for? It puts the next print statement on a new line in the console. Without it, the console would print out each menu item all in one line. To see how it works, try removing n.

Your program needs to be able to read user input and determine which set of code to execute. You will use if and else if statements to check if the user input is 1,2,3,4 or 5.

Make sure you’re still in the while loop, and then set your drone’s roll, pitch, yaw, and throttle to 0. That way, they will all be ready for each maneuver you program! Next, create a variable called option to store input(). In the parameters for input(), write “Select an option: “. This will print the command, and when the user inputs a number, it will be stored as an option and called later on.

This is what you should have now:

drone.set_throttle(0)

drone.set_roll(0)

drone.set_yaw(0)

drone.set_pitch(0)


option = int(input("Select an option: “))

Depending on the user input, your CoDrone will fly a different pattern! The best way to set this up is with conditionals. Have your drone take off, and then for option 1, set up an if statement and include your drone’s maneuver. 

    if option == 1:
        drone.takeoff()
        drone.set_yaw(30)
        drone.move(2)

For options 2 through 4, use else if statements, and then include drone maneuvers.

    elif option == 2:
        drone.takeoff()
        drone.triangle()

    elif option == 3:
        drone.takeoff()
        drone.square()

    elif option == 4:
        drone.takeoff()
        drone.sway()

For option 5, use another else if statement again, but include a print command that says, “You have quit the menu” and then a break. This will exit the loop.

    elif option == 5:
        print("You have quit the menu.")
        break

Next, include an else statement that will work when an invalid user input (like a number outside 1-5) is entered. This is not necessary, but it is good programming practice to provide feedback to the user when they have input something incorrect. 

    else:
        print("Not a valid input. Try again.")

Finally, have your drone land and then (this is optional) include a print command that says “Done.”

    drone.land()
print("Done")

Your final program should look something like this:

from codrone_edu.drone import *

drone = Drone()
drone.pair()

while True:

    print("Menu: ")
    print("1. Spin Around n"
        "2. Fly in a triangle n"
        "3. Fly in a square n"
        "4. Sway n"
        "5. Quit n")


    drone.set_throttle(0)
    drone.set_roll(0)
    drone.set_yaw(0)
    drone.set_pitch(0)


    option = input("Select an option: ")

    if option == "1":
        drone.takeoff()
        drone.set_yaw(30)
        drone.move(2)

    elif option == "2":
        drone.takeoff()
        drone.triangle()

    elif option == "3":

        drone.takeoff()
        drone.square()

    elif option == "4":

        drone.takeoff()
        drone.sway()

    elif option == "5":

        print("You have quit the menu.")
        break

    else:
        print("Not a valid input. Try again.")

    drone.land()

print("Done")
drone.close()

For this challenge, you will need to create a program that does the following:

1. Takes in a value between 2 and 6 (2 is a circle)
2. Prints out a menu with each value option
3. Uses that value to make the appropriate sided polygon (for example, 4 would make the drone fly in a square)
4. Takeoff before requesting user input
5. Land once the polygon is completed.
6. Use at least one sequence in the program.

It is strongly recommended that you go back to the for loops lesson and use your polygon program that you have already written and modify it to fit these new requirements. (We call this code reuse, and it is a popular concept in the professional world of programming)

In this lesson, you learned about user input! User input is important for programs that rely on user interaction and allowing users to make decisions in a program.