To set up the Uplink, you need to enable it in the Anvil IDE,
pip install a Python library, then write three lines of
The Anvil uplink is a library you add to your own code, running outside Anvil. It connects securely to the Anvil server, and allows your Anvil app to call functions in your project. You can also call server modules within your app from your uplinked code. The Anvil uplink works through most firewalls, as it initiates the connection to the Anvil server.
Start by selecting the Anvil Uplink in the Gear Menu :
It will display an authentication key that you will use to connect your code to your app.
Install the Python library on your machine:
pip install anvil-uplink
Start by adding the Uplink to your app, by clicking the + button in the sidebar menu, and choosing Uplink:
If you haven’t already deployed your app, you’ll see a button labelled Add Uplink keys. You’ll need to click it before moving on to the next step:
If you’ve already deployed your app, you’ll see all your deployment environments.
Click one to select it, and click Enable next to Server Uplink Key or Client Uplink Key (learn about the difference). This will create a secret key that you can use to connect external code to your application:
In your local Python code, call
anvil.server.connect() with your app’s connection key in order to link this program with your Anvil app. This establishes a connection in a background thread and will keep attempting to reconnect to Anvil if it fails (for instance, if you lose your local internet access temporarily).
# In a script on your own machine (or anywhere) import anvil.server anvil.server.connect("[YOUR UPLINK KEY]") @anvil.server.callable def get_file(): # Return a file from this local machine return anvil.media.from_file("./image.jpg", "image/jpeg") anvil.server.wait_forever()
anvil.server.wait_forever() is just a useful shortcut to keep your Python script running, to allow your app to
anvil.server.call functions in it.
You can use any other way to keep the process alive - for instance,
anvil.server.connect("[YOUR UPLINK KEY]") @anvil.server.callable def get_file(): return anvil.media.from_file("./image.jpg", "image/jpeg") while True: # keep the process alive to respond sleep(1)
You can even run the Uplink in a Python REPL!
Sometimes you may only want to connect your code temporarily using the Anvil Uplink. To safely close down an Uplink connection, just call
anvil.server.disconnect() when you are ready to end the connection.
import anvil.server def open_anvil_connection(uplink_key): anvil.server.connect(uplink_key) do_something_cool_using_uplink() anvil.server.disconnect()
This can be done within a context manager. For example:
import anvil.server from contextlib import contextmanager @contextmanager def open_anvil_connection(uplink_key): anvil.server.connect(uplink_key) yield anvil.server.disconnect()
You can then use it in a
with statement which politely closes down the connection when it’s done:
with open_anvil_connection("[YOUR UPLINK KEY]"): data = anvil.server.call("some_remote_function") results = perform_local_calculation(data) anvil.server.call("write_back_crunched_data", results)
Custom setup code
Sometimes, it is necessary to initialise an uplink’s session before interacting with your app. For example, a client (unprivileged) uplink process might need to authenticate with the app before it will be allowed to perform certain operations.
If you pass the
init_session= keyword parameter to
anvil.server.connect, it will be called after the uplink connection is established, but before any other interaction (such as server calls or function registrations) have occurred. If connection is lost and the uplink library reconnects,
init_session will be called again before any interaction occurs. This guarantees that
init_session has completed whenever you interact with the Anvil app.
import anvil.users def setup(): anvil.users.login_with_email("firstname.lastname@example.org", "MY_PASSWORD") anvil.server.connect("[YOUR UPLINK KEY]", init_session=setup) anvil.server.call("some_func")
init_session raises an exception, all subsequent Anvil interactions will fail and raise exceptions.
Suppressing connection messages
By default, the Uplink prints some output during the connection phase:
Connecting to wss://anvil.works/uplink Anvil websocket open Authenticated OK
You can pass an optional keyword argument “
anvil.server.connect() to suppress this. Errors (such as connection failure and reconnection attempts) will still be printed.
# Connect without printing to console anvil.server.connect("[YOUR UPLINK KEY]", quiet=True)
Do you still have questions?
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