3B: Lists

In Python, lists store and organize data of the same type without you having to create multiple variables. For example, this list could represent your classes:

subjects = ['algebra', 'english',  'computer science', 'history', 'biology']

Important: these lists are ordered. This means that each item has a position in the list called the index, which is an integer that refers to its position in the list starting from 0. The first element in the list is at index 0 because it is 0 steps away from the beginning of the list. In any case that involves counting, you will be starting from 0, so don’t forget!

Having an index is like having the address of where your information lives. A particular value can be accessed by the name of the list and its index:

listName[index]

So if you wanted to access your class list above, it would look like this:

subjects[index]

To explain lists, we’re going to be using the buzzer on your CoDrone Mini’s remote! Since musical notes are part of groups called scales, you will be able to hear your lists in action.

The first thing you need to do is play one note. Import the CoDrone Mini and note libraries, create the drone object, and pair to your CoDrone Mini. Next, play the note! The first parameter is the note itself, and the second parameter is how many seconds it will play for. We used middle C for our program, but you can use whatever note you like.

Try this out and see what the note sounds like!

import CoDrone_mini

from CoDrone_mini import Note

drone = CoDrone_mini.CoDrone()

drone.pair()


drone.play_note(Note.C4, 0.5)

Unless you know music really well, there’s a good chance you’re not sure the names of the notes you will need to use. Instead, you can use frequency! In music, and sound in general, frequency is the number of pulses or vibrations per second, and it’s measured in hertz. The higher the frequency, the higher the pitch, or sound, is. 

To try this out, use the program that you made in the last step. However, replace  Note.C4 with  261 , and then try it out. Did you get the same thing?

Your program should look like this:

import CoDrone_mini

from CoDrone_mini import Note

drone = CoDrone_mini.CoDrone()

drone.pair()


drone.play_note(261, 0.5) #261 Hz is Note.C4

Use a frequency table like this one to find the frequencies of more notes, and then experiment with them in your program! Just as a warning, decimal points will not work in the frequency parameter, so you will need to round to the closest whole number.

Compose your own song using notes or frequencies! To give your song some rhythm, use the  time.sleep() function between notes or groups of notes. Try our program out and then write yours!

import CoDrone_mini

from CoDrone_mini import Note

Import time

drone = CoDrone_mini.CoDrone()

drone.pair()


drone.play_note(Note.C4, 0.5)

drone.play_note(Note.D4, 0.5)

time.sleep(0.25)

drone.play_note(Note.E4, 0.5)

drone.play_note(Note.F4, 0.5)

time.sleep(0.5)

drone.play_note(Note.G4, 0.5)

Now that you’ve made some music with the remote, let’s get back to lists.

In music, scales are groups of eight notes that increase or decrease in pitch, and they typically start with a C note. What you will be doing in this activity is making a list of notes for a C-major scale and then using that list to play specific notes.

After importing the CoDrone Mini and note libraries, creating the drone object, and pairing to CoDrone Mini, create a list called  notes . Next, add in the notes for your scale. Your scale can start with C3, C4, C5, C6, or C7, and then go all the way up or down to the next octave, or the note that’s 8 steps away from the first note.

notes = [Note.C3, Note.D3, Note.E3, Note.F3, Note.G3, Note.A3, Note.B3, Note.C4]

Once the list is finished, you can practice playing a specific note from the list. This is what that line of code will look like:

drone.play_note(notes[0], 0.5) # change the index to change notes

Remember that counting starts at 0, so  notes[0] will play the first note,  notes[1] will play the second, and so on.

This is what your program should look like:

import CoDrone_mini

from CoDrone_mini import Note

drone = CoDrone_mini.CoDrone()

drone.pair()


notes = [Note.C3, Note.D3, Note.E3, Note.F3, Note.G3, Note.A3, Note.B3, Note.C4]


drone.play_note(notes[0], 0.5) # change the index to change notes

Lists can be long, and there may be times when you forget how many items your list has! To help with this, you can use the  len() function. It will print out the number of items in your list.

Try it out by using print(len(notes))after your list in your last program. Does your list have the correct amount of items?

Your program should look something like this:

import CoDrone_mini

from CoDrone_mini import Note

drone = CoDrone_mini.CoDrone()

drone.pair()


notes = [Note.C3, Note.D3, Note.E3, Note.F3, Note.G3, Note.A3, Note.B3, Note.C4]


print(len(notes))

You can use a loop to play every note in your list one time for 0.5 seconds. To do this, use your code from the last step, but take out the print command. 

Use a for loop that will access the length of the notes list and then play them for 0.5 seconds each. Since the range of the for loop is the length of the list, each note will play only one time. 

This is what your program should look like:

import CoDrone_mini

from CoDrone_mini import Note

drone = CoDrone_mini.CoDrone()

drone.pair()


notes = [Note.C3, Note.D3, Note.E3, Note.F3, Note.G3, Note.A3, Note.B3, Note.C4]


for i in range(len(notes)):

   drone.play_note(notes[i], 0.5)

Just like variables, you can have more than one list in your program! These are great to have if you have different data types or want to keep your items categorized. For this step, you will be adding another list for note duration.

Use your program from the last step and then create a list called  duration . This list should be the same size as the notes list, so include eight note durations. They can all be different, or some can be the same. Just remember that these durations are in seconds.

Next, add a for loop to play both the notes and their durations, and then run your program to see what it sounds like! You can always add or subtract items from their lists. Just make sure you have the same amount of items in both.

Your program should look something like this:

import CoDrone_mini

from CoDrone_mini import Note

drone = CoDrone_mini.CoDrone()

drone.pair()


notes = [Note.C3, Note.D3, Note.E3, Note.F3, Note.G3, Note.A3, Note.B3, Note.C4]

duration = [0.1, 0.1, 0.25, 0.25, 0.25, 0.1, 0.1, 0.5]


for i in range(len(notes)):

   drone.play_note(notes[i], duration[i])

Challenge: Make Some Noise

Now that you know how to use lists for both notes and durations, see if you can program your drone’s remote to play a popular song! This can be something short or a long classical symphony. If you know how to read sheet music, you can use that, but you can also use trial and error to figure notes out!