penne 0.2.3

Python Client Library for NOODLES Protocol

PENNE

Python Client for NOODLES protocol
(Python Encoded Native NOODLES Endpoint)

Description

The client library is based on the NOODLES messaging protocol for communicating with serverside data visualisation applications. The client uses a websocket connection to send CBOR encoded messages. To customize its implementation, the library offers hooks in the form of delegates classes which can be extended and overwritten.

How does the client work?

When a message is received from the server, the client passes the CBOR encoded message to a handler function which uses the message's ID to process it accordingly. Based on this ID, the message can be classified as either a create, delete, update, reply, or invoke message. Upon receiving a create message, the handler creates a new delegate for that object which is then stored in the client's state. Delete and update messages manipulate delegates in the client's state as expected. Reply messages indicate whether a method was invoked on the server successfully, and then a callback function can be executed if applicable. Lastly, invoke messages represent signals from the server which are being called on a delegate. The handler essentially sends this signal to the target delgate so it can call a corresponding function.

To send a message, the user calls a method on a delegate. This method wraps an injected method from the server, and the client can send a message invoking the method.

A diagram representing the simplified relationships between the client, server, and delegates is depicted below.

flowchart LR;
    User-- Request to Invoke Method -->Delegate;
    User-- Create Custom Delegates --> Client;
    User-- Create New Plot --> Client;
    Delegate-- Call Injected Method -->Client;
    Client-- Send Invoke Method Message -->Server;
    Server-- Message -->Client;
    Client-- Create w/ Injection -->Delegate;
    Client-- Update -->Delegate;
    Client-- Invoke Signal -->Delegate;
    Delegate-- Show current state -->User;

Working with delegates

What are delegates?

NOODLES messages deal with many different objects ranging from tables and plots to lights and materials. To help with using these objects, each type has its own delegate class. Each object in a scene corresponds with an instance of a delegate which is stored in the client's state. Delegates provide methods specific to each type of object.

Note: PENNE currently offers support primarily for the table delegate class

How can I use custom delegates?

To work with your own delegates, use a custom delegate hash as an argument in create_client(). To overide a default delegate, use the same key in your dictionary. The library also provides a generic Delegate class that should be used as the parent class for any delegate. An example of a custom delegate is included in test_client.py. Here, the delegate class inherits from TableDelegate and uses the pandas library to add table and plotting functionality.

How do you call methods on a delegate?

Once instantiated, delegates are injected with methods designated by the server. These methods can be called by using public methods on the delegate that essentially wrap the injected ones. Once the method is invoked, the server will respond with a signal that updates the client. Each signal is linked to a method in the delegate which keeps the state of the client up to date. To customize the client's behavior, these methods can be overwritten in a custom delegate. Each public method also accepts a callback function to be executed once a response is received from the server. This way, method calls can be chained together and run in sequence. An example is provided in test_client.py.

Tables

The table delegate comes with several built in methods covering basic table manipulation. The delegate includes...

request_insert(col_list: list=None, row_list: list=None, on_done=None)
request_remove(keys: list, on_done=None)
request_update(data_frame: pandas.DataFrame, on_done=None)
request_clear(on_done=None)
request_update_selection(name: str, keys: list, on_done=None)

Once invoked, signals from the server will update the table in the delegate. When using these methods, the user has the option of including a callback function that will execute once complete.

Getting Started

1. Install the library

pip install penne

2. Create a client using create_client(address, delegate_hash)

client: penne.Client = penne.create_client("ws://localhost:50000")

• (Optional) use delegate hash to map custom delegates
• Note: make sure to close client thread at some point - client.thread.join()

3. Explore and manipulate data on the server using client or delegate methods

• call show_methods() on the client to see a list of available methods with documentation
• call show_methods() on a delegate to see a list of available methods for that instance