1.5: The Go Function (Abstraction)

By the end of this lesson, you should be able to:

• Incorporate your knowledge of creating a complete program from Island 1 to build a full flight path for the drone including takeoff and landing.
• Utilize the go() method to make your drone fly to a specific location
• Explain what abstraction is and how it is used in programming
• Describe the benefits of abstraction in programming

In this lesson, you will complete the following steps. Make sure that you demonstrate your completed code to your instructor after each step:

1. Getting Started
2. Multitasking Using Two Flight Commands
3. An Easier Way: The go() command
4. Challenge 1: Puddle Jumper
5. Challenge 2: Obstacle Course

Before we learn how drones move, we need to have a program created for testing movement. To do this, follow the steps below:

1. Open Pycharm
2. Right click on the 2_Flight_Directions folder you created in lesson 1 and click New -> Python File
3. Name the file multitasking
4. Enter the commands you learned from the previous lesson to pair with the drone, take off, and land. (Hint: You can go back to the previous lesson’s folder to look at what you wrote if you can’t remember) 

You are now ready to start testing some of the movements that your drone can perform!

As we learned in the Drone Tango, the drone can move in a single direction or multiple directions at once. Keep in mind that the drone cannot do two of the same command at once. For example, this code would result in the drone only moving backwards, not forwards. 

drone.set_pitch(20)
drone.set_pitch(-20)
drone.move(1)

 

However, we can combine different flight commands to make the drone move in more complex directions such as flying at an angle instead of a straight line. To see an example of how this works, create a new file called multiple.py and run the code below. 

import CoDrone_mini
drone = CoDrone_mini.CoDrone()
drone.pair()
drone.takeoff()       # takeoff for 2 seconds
drone.set_pitch(30)    # Set positive pitch to 30% power
drone.set_roll(-30)    # Set negative roll to 30% power   
drone.move(2)         # forward and left for 2 seconds
drone.land()          # lands the CoDrone
drone.close()         # disconnects CoDrone

What you should have observed was the drone moving forward and to the left at the same time! Take a minute and play around with the different movement commands and see what you can do. See if you can answer the following when you are done:

1. What happens if you use pitch, roll, and yaw all at the same time?
2. Can you combine throttle and pitch or roll?
3. What if you wanted to make the drone fly in a semicircle, what commands would you combine?
4. What is the disadvantage of having to reset the movement values after each movement?

The last question in the previous step asked you about the disadvantages of using flight commands for drone navigation. You may have noticed the following:

• It is easy to forget to reset the values.
• It makes it harder to separate movements
• It requires extra lines of code
• It is not very intuitive

When we see issues like extra code and difficulty to implement or understand, as programmers we want to apply a concept called ABSTRACTION. Abstraction is the process of hiding extra or confusing features to reduce complexity and increase efficiency. So when we see, as a programmer, that commands are repetitive or difficult to use, we create new commands or features that make our code simpler to use. This is what the go() command does. It takes the code we learned from the individual flight commands and the move() command and abstracts  them into a single, easier to use command. This is what the function looks like:

drone.go(direction, duration, power)

This is what each part means:

• Direction: where the drone will fly. You can use FORWARD, BACKWARD, LEFT, RIGHT, UP, and DOWN, but make sure you type in all caps like you see here. You will also need to type Direction before it, so it will look like Direction.FORWARD.
• Duration: how long the movement will happen in seconds. You can leave it as blank, zero, or any positive number. If duration is zero, it runs indefinitely. If duration has no number, it automatically sets to 1. If you put any positive number, duration is equal to that value.
• Power: the speed of the drone. It can be any number between 0-100, with 0 being no power and 100 being full power. If power has no number, it will default to 50.

Here are some examples:

drone.go(Direction.UP, 3, 75) # go up for 3 seconds at 75% power
drone.go(Direction.FORWARD)   # go forward for 1 second at 50% power
drone.go(Direction.LEFT, 6)   # go left for 6 seconds at 50% power

If you want to use drone.go()in your programs, you’ll need to include this line at the top, right underneath import CoDrone_mini:

from CoDrone_mini import Direction

 

This tells the program to look for and use the specific part of the CodDrone package called Direction because it is not used by default. 

After that, you’re good to go! Try using drone.go() in the program you wrote for Step 3 in place of drone.set() and drone.move(). What happened?

Once you have that completed, try going back and redoing the box flights in Challenge 1. When you are done you should be able to answer the following questions:

1. Is using the go() command easier than the set() commands for this challenge? Why or why not?
2. Did you use fewer lines of code with the go() command instead of the set() commands?
3. Do you think there is a time to use set() commands versus a time to use go() commands? If so, describe examples of when to use each set of commands.

Have two tables or chairs 2 feet apart. The goal is to have the CoDrone Mini take off from one chair, land on the other, turn around, fly back, and then land at the starting point. It should look like this:

A -> B then B -> A

Rules:

• The CoDrone Mini should always fly forward between chairs.
• If you succeed, move the tables or chairs an additional 2 feet apart. Continue adding 2 feet for every success until you reach the ends of the room.

Hint: You can use drone.land() in the middle of the code and take off again.

For this challenge, work with a partner or a group of 3 to design an obstacle course. The course must contain between 5 and 10 obstacles and must be achievable with the commands you know so far. Once you have designed the course, work together to have your drone complete the course in the fastest time with the fewest lines of code.

If you are doing this as a part of a class, complete the next steps:

1. Come up with a name for your group.
2. Take a piece of paper and write your team name, best time, and number of lines of code and tape it or place it near the beginning of your obstacle course.
3. Go and try to beat other team’s records for their obstacle courses. The teams with the least lines of code and the fastest time win!

Rules:

• Between 5-10 obstacles in course
• Can only use commands you already know
• Drones must complete all obstacles for a time to count