EVI Python Quickstart Guide

Environment setup

Before starting the project, it is essential to set up the development environment.

Creating a virtual environment (optional)

Setting up a virtual environment is a best practice to isolate your project’s dependencies from your global Python installation, avoiding potential conflicts.

You can create a virtual environment using either Python’s built-in venv module or the conda environment manager. See instructions for both below:

$
python -m venv evi-env

$
source evi-env/bin/activate

Package dependenices

There are two package dependencies for using EVI:

1. Hume Python SDK (required)

The hume[microphone] package contains the Hume Python SDK. This guide employs EVI’s WebSocket and message handling infrastructure as well as various asynchronous programming and audio utilities.

$
pip install "hume[microphone]"

2. Environment variables (recommended)

The python-dotenv package contains the logic for using environment variables to store and load sensitive variables such as API credentials from a .env file.

$
pip install python-dotenv

In sample code snippets below, the API key, Secret key, and an EVI configuration id have been saved to environment variables.

System dependencies

For audio playback and processing, additional system-level dependencies are required. Below are download instructions for each supported operating system:

$
brew install ffmpeg

Dependency imports

The following import statements are used in the example project to handle asynchronous operations, environment variables, audio processing, and communication with the Hume API:

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import asyncio
2
import base64
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import datetime
4
import os
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from dotenv import load_dotenv
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from hume.client import AsyncHumeClient
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from hume.empathic_voice.chat.socket_client import ChatConnectOptions, ChatWebsocketConnection
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from hume.empathic_voice.chat.types import SubscribeEvent
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from hume.empathic_voice.types import UserInput
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from hume.core.api_error import ApiError
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from hume import MicrophoneInterface, Stream

Defining a WebSocketInterface class

The WebSocketInterface class manages the EVI WebSocket connection, allowing you to define behavior on opening, closing, receiving a message, and encountering an error. Below are its key methods:

Authentication

In order to establish an authenticated connection, we instantiate the Hume client with our API key and include our Secret key in the query parameters passed into the WebSocket connection.

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async def main() -> None:
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  # Retrieve any environment variables stored in the .env file
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  load_dotenv()
4
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  # Retrieve the API key, Secret key, and EVI config id from the environment variables
6
  HUME_API_KEY = os.getenv("HUME_API_KEY")
7
  HUME_SECRET_KEY = os.getenv("HUME_SECRET_KEY")
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  HUME_CONFIG_ID = os.getenv("HUME_CONFIG_ID")
9
10
  # Initialize the asynchronous client, authenticating with your API key
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  client = AsyncHumeClient(api_key=HUME_API_KEY)
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  # Define options for the WebSocket connection, such as an EVI config id and a secret key for token authentication
14
  options = ChatConnectOptions(config_id=HUME_CONFIG_ID, secret_key=HUME_SECRET_KEY)
15
  
16
  # ...

Connecting to EVI

With the Hume client instantiated with our credentials, we can now establish an authenticated WebSocket connection with EVI and pass in our handlers.

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async def main() -> None:
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  # ...
3
  # Define options for the WebSocket connection, such as an EVI config id and a secret key for token authentication
4
  options = ChatConnectOptions(config_id=HUME_CONFIG_ID, secret_key=HUME_SECRET_KEY)
5
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  # Instantiate the WebSocketInterface
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  websocket_interface = WebSocketInterface()
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  # Open the WebSocket connection with the configuration options and the interface's handlers
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    async with client.empathic_voice.chat.connect_with_callbacks(
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      options=options,
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      on_open=websocket_interface.on_open,
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      on_message=websocket_interface.on_message,
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      on_close=websocket_interface.on_close,
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      on_error=websocket_interface.on_error
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    ) as socket:
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      # Set the socket instance in the handler
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      websocket_interface.set_socket(socket)
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      # ...

Handling audio

The MicrophoneInterface class captures audio input from the user’s device and streams it over the WebSocket connection.

Audio playback occurs when the WebSocketInterface receives audio data over the WebSocket connection in its asynchronous byte stream from an audio_output message.

In this example, byte_strs is a stream of audio data that the WebSocket connection populates.

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async def main() -> None:
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  # Open the WebSocket connection with the configuration options and the interface's handlers
3
  async with client.empathic_voice.chat.connect_with_callbacks(...) as socket:
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    # Set the socket instance in the handler
5
    websocket_interface.set_socket(socket)
6
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    # Create an asynchronous task to continuously detect and process input from the microphone, as well as play audio
8
    microphone_task = asyncio.create_task(MicrophoneInterface.start(socket, byte_stream=websocket_interface.byte_strs))
9
    
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    # Await the microphone task
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    await microphone_task

Specifying a microphone device

You can specify your microphone device using the device parameter in the MicrophoneInterface object’s start method.

To view a list of available audio devices, run the following command:

python -c "import sounddevice; print(sounddevice.query_devices())"

Below is an example output:

$
   0 DELL U2720QM, Core Audio (0 in, 2 out)
>
   1 I, Phone 15 Pro Max Microphone, Core Audio (1 in, 0 out)
>
>  2 Studio Display Microphone, Core Audio (1 in, 0 out)
>
   3 Studio Display Speakers, Core Audio (0 in, 8 out)
>
   4 MacBook Pro Microphone, Core Audio (1 in, 0 out)
>
<  5 MacBook Pro Speakers, Core Audio (0 in, 2 out)
>
   6 Pro Tools Audio Bridge 16, Core Audio (16 in, 16 out)
>
   7 Pro Tools Audio Bridge 2-A, Core Audio (2 in, 2 out)
>
   8 Pro Tools Audio Bridge 2-B, Core Audio (2 in, 2 out)
>
   9 Pro Tools Audio Bridge 32, Core Audio (32 in, 32 out)
>
  10 Pro Tools Audio Bridge 64, Core Audio (64 in, 64 out)
>
  11 Pro Tools Audio Bridge 6, Core Audio (6 in, 6 out)
>
  12 Apowersoft Audio Device, Core Audio (2 in, 2 out)
>
  13 ZoomAudioDevice, Core Audio (2 in, 2 out)

If the MacBook Pro Microphone is the desired device, specify device 4 in the Microphone context. For example:

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# Specify device 4 in MicrophoneInterface
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MicrophoneInterface.start(socket, device=4, allow_user_interrupt=True, byte_stream=websocket_interface.byte_strs)

For troubleshooting faulty device detection - particularly with systems using ALSA, the Advanced Linux Sound Architecture, the device may also be directly specified using the sounddevice library:

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# Directly import the sounddevice library
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import sounddevice as sd
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4
# Set the default device prior to scheduling audio input task
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sd.default.device = 4

Allowing interruption

The allow_interrupt parameter in the MicrophoneInterface class allows control over whether the user can send a message while the assistant is speaking:

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# Specify allowing interruption
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MicrophoneInterface.start(socket, allow_user_interrupt=True, byte_stream=websocket_interface.byte_strs)

• allow_interrupt=True: Allows the user to send microphone input even when the assistant is speaking. This enables more fluid, overlapping conversation.
• allow_interrupt=False: Prevents the user from sending microphone input while the assistant is speaking, ensuring that the user does not interrupt the assistant. This is useful in scenarios where clear, uninterrupted communication is important.

Asynchronous event loop

Initialize, execute, and manage the lifecycle of the asynchronous event loop, making sure that the main() coroutine and its runs effectively and that the application shuts down cleanly after the coroutine finishes executing.

1
asyncio.run(main())