Use python3 to program your LEGO Mindstorms EV3. The program runs on the local host and sends direct commands to the EV3 device. It communicates via bluetooth, wifi or USB. I wrote a blog about this code.

There is no need to boot the EV3 device from a SD Card or manipulate its software. You can use it as it is, the EV3 is designed to execute commands which come from outside.

The code consists of the following modules:

• ev3.py
  Base class EV3, that represents the LEGO EV3 device.
• ev3_file.py
  FileSystem, subclass of EV3. Access to EV3's filesystem.
• ev3_sound.py
  Jukebox, subclass of EV3. Combines sound and LED light effects, plays music.
• ev3_vehicle.py
  TwoWheelVehicle, subclass of EV3. Precise movements of a vehicle with two drived wheels.
• task.py
  Organizes tasks. Allows parallel and sequential execution of functions.

This program communicates via USB with an EV3 device (mac-address: '00:16:53:42:2B:99') and plays a tone with a frequency of 440 Hz for a duration of 1 sec.

#!/usr/bin/env python3

import ev3

my_ev3 = ev3.EV3(protocol=ev3.USB, host='00:16:53:42:2B:99')
my_ev3.verbosity = 1
ops = b''.join([
    ev3.opSound,
    ev3.TONE,
    ev3.LCX(1),    # VOLUME
    ev3.LCX(440),  # FREQUENCY
    ev3.LCX(1000), # DURATION
])
my_ev3.send_direct_cmd(ops)

Its output:

11:48:31.188008 Sent 0x|0E:00|2A:00|80|00:00|94:01:01:82:B8:01:82:E8:03|

This shows the direct command, which was sent to the EV3 device.

Class Jukebox of module ev3_sound has a method play_tone, which also plays tones:

#!/usr/bin/env python3

import ev3, ev3_sound

jukebox = ev3_sound.Jukebox(protocol=ev3.BLUETOOTH, host='00:16:53:42:2B:99')
jukebox.verbosity = 1
jukebox.play_tone("a'", duration=1)

This program communicates via Bluetooth and sends a direct command too. Its output:

11:55:11.324701 Sent 0x|0E:00|2A:00|80|00:00|94:01:01:82:B8:01:82:E8:03|