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Wave scripts are plain Python programs. Wave apps are ASGI programs. You can develop, debug and test them from the command-line, from the Python REPL, or from your favorite text editor.

Both PyCharm Community Edition and Visual Studio Code are excellent for Python programming.


At the time of writing, PyCharm's type-checking and error-detection is superior to Visual Studio Code's Python plugin.

Getting started

The simplest way to get started in either PyCharm or Visual Studio Code is the same:

  1. Create a working directory.
  2. Set up a Python virtual environment.
  3. Install the h2o-wave package.
  4. Open the directory in your IDE.
mkdir $HOME/wave-apps
cd $HOME/wave-apps
python3 -m venv venv
./venv/bin/pip install h2o-wave

Using PyCharm

  1. Launch PyCharm
  2. Click "File" -> "Open...", then choose $HOME/wave-apps.
  3. Right-click on wave-apps in the "Project" tree, then click "New" -> "Python File".
  4. Enter a file name, say,
  5. Write some code (see sample below).
  6. Right-click anywhere inside the file and choose "Run foo" or "Debug foo".

To make Wave app development easier, we suggest installing our PyCharm plugin. If you want to learn more about all of its features check out this blog post.

Using Visual Studio Code

  1. Launch Visual Studio Code
  2. Click "File" -> "Open...", then choose $HOME/wave-apps.
  3. Click "File" -> "New File"; save the file as, say,
  4. You should now get a prompt asking if you want to install extensions for Python. Click "Install".
  5. Write some code (see sample below).
  6. Hit Ctrl+F5 to run, or F5 to debug.

To make Wave app development easier, we suggest installing our VSCode extension. If you want to learn more about all of its features check out this blog post.

Debugging Apps

To debug Wave apps, set your IDE or editor's configuration to execute the command python -m h2o_wave run --no-reload foo instead of python


The command wave run --no-reload foo is equivalent to python -m h2o_wave run --no-reload foo.

Debug in PyCharm

  • Open the "Run/Debug Configurations" dialog for your script.
  • Under "Configuration", change the "Script path" dropdown to "Module name".
  • Set "Module name" to h2o_wave.
  • Set "Parameters" to run foo (assuming your app's source code is in

Debug in Visual Studio Code

  • Run "Open launch.json" command (cmd + shift + P).
  • Add the configuration listed below.
  • Go to Debug pane, select your newly added config and run it to start debugging.
"name": "Debug Wave App",
"type": "python",
"request": "launch",
// Path to your wave installation, usually inside virtual env.
"program": "${workspaceFolder}/venv/bin/wave",
// Path to python you are using, usually inside virtual env.
"python": "${workspaceFolder}/venv/bin/python",
"args": [

Using OpenID Connect

You can set up a local Keycloak instance for developing apps that use OpenID Connect, OAuth 2.0, or SAML 2.0 for authentication, single sign-on, and so on.

Run Keycloak

First, create a local directory to persist all the realms, clients, and users you'll be adding to Keycloak:

mkdir ~/.keycloak

Run Keycloak using Docker:

docker run \
-p 8080:8080 \
--volume ~/.keycloak:/opt/jboss/keycloak/standalone/data \ \

Keycloak should now be running at http://localhost:8080/.

Add a client

Next, create a client in Keycloak to represent our app:

  • Go to Keycloak at http://localhost:8080/admin.
  • Log in with username admin, password admin.
  • In the top left, click on Clients
    • Click the Create client button to create a new client.
    • Set Client ID to wave.
    • Click "Next".
    • Change the "Client authentication" to On to change access type of the to confidential.
    • Click Next.
    • Set Valid Redirect URIs to * (never do this in production).
    • Click Save.
    • Click the Credentials tab.
    • Copy the Client secret field (e.g. xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx).

Add test users

Next, add one or more users to Keycloak:

  • In the top left, click on Users.
    • Click the Add User button to create a new user.
    • Set the Username field.
    • Click Create.
    • Go to the Credentials tab.
    • Click Set password.
    • Set the password fields.
    • Change Temporary to Off.
    • Click Save.

You can also use admin user for logging in with credentials admin/admin if you just need a quick testing.

Point Wave to Keycloak

We're ready to use Keycloak now. Make sure you log out of Keycloak, otherwise you'll be logged in as admin when you access your Wave app!

Finally, start the Wave daemon with the following -oidc- command line arguments (use the client secret you copied above):

./waved \
-oidc-client-id wave \
-oidc-client-secret xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx \
-oidc-redirect-url http://localhost:10101/_auth/callback \
-oidc-provider-url http://localhost:8080/realms/master \
-oidc-end-session-url http://localhost:8080/realms/master/protocol/openid-connect/logout

Now, when you launch and access your Wave app, you should see a OpenID prompt which you can use to log in one of the users you created in Keycloak.