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455 lines
17 KiB
Markdown
455 lines
17 KiB
Markdown
# pydase (Python Data Service) <!-- omit from toc -->
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[](https://opensource.org/licenses/MIT)
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[](https://pydase.readthedocs.io/en/latest/?badge=latest)
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`pydase` is a Python library for creating data service servers with integrated web and RPC servers. It's designed to handle the management of data structures, automated tasks, and callbacks, and provides built-in functionality for serving data over different protocols.
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- [Features](#features)
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- [Installation](#installation)
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- [Usage](#usage)
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- [Defining a DataService](#defining-a-dataservice)
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- [Running the Server](#running-the-server)
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- [Accessing the Web Interface](#accessing-the-web-interface)
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- [Connecting to the Service using rpyc](#connecting-to-the-service-using-rpyc)
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- [Understanding the Component System](#understanding-the-component-system)
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- [Built-in Type and Enum Components](#built-in-type-and-enum-components)
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- [Method Components](#method-components)
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- [DataService Instances (Nested Classes)](#dataservice-instances-nested-classes)
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- [Custom Components (`pydase.components`)](#custom-components-pydasecomponents)
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- [Extending with New Components](#extending-with-new-components)
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- [Understanding Service Persistence](#understanding-service-persistence)
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- [Understanding Tasks in pydase](#understanding-tasks-in-pydase)
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- [Understanding Units in pydase](#understanding-units-in-pydase)
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- [Changing the Log Level](#changing-the-log-level)
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- [Documentation](#documentation)
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- [Contributing](#contributing)
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- [License](#license)
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## Features
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<!-- no toc -->
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* [Simple data service definition through class-based interface](#defining-a-dataService)
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* [Integrated web interface for interactive access and control of your data service](#accessing-the-web-interface)
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* [Support for `rpyc` connections, allowing for programmatic control and interaction with your service](#connecting-to-the-service-using-rpyc)
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* [Component system bridging Python backend with frontend visual representation](#understanding-the-component-system)
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* [Saving and restoring the service state for service persistence](#understanding-service-persistence)
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* [Automated task management with built-in start/stop controls and optional autostart](#understanding-tasks-in-pydase)
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* [Support for units](#understanding-units-in-pydase)
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<!-- * Event-based callback functionality for real-time updates
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* Support for additional servers for specific use-cases -->
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## Installation
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<!--installation-start-->
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Install pydase using [`poetry`](https://python-poetry.org/):
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```bash
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poetry add pydase
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```
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or `pip`:
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```bash
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pip install pydase
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```
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<!--installation-end-->
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## Usage
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<!--usage-start-->
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Using `pydase` involves three main steps: defining a `DataService` subclass, running the server, and then connecting to the service either programmatically using `rpyc` or through the web interface.
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### Defining a DataService
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To use pydase, you'll first need to create a class that inherits from `DataService`. This class represents your custom data service, which will be exposed via RPC (using rpyc) and a web server. Your class can implement class / instance attributes and synchronous and asynchronous tasks.
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Here's an example:
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```python
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from pydase import DataService, Server
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class Device(DataService):
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_current = 0.0
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_voltage = 0.0
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_power = False
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@property
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def current(self) -> float:
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# run code to get current
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return self._current
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@current.setter
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def current(self, value: float) -> None:
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# run code to set current
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self._current = value
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@property
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def voltage(self) -> float:
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# run code to get voltage
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return self._voltage
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@voltage.setter
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def voltage(self, value: float) -> None:
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# run code to set voltage
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self._voltage = value
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@property
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def power(self) -> bool:
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# run code to get power state
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return self._power
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@power.setter
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def power(self, value: bool) -> None:
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# run code to set power state
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self._power = value
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def reset(self) -> None:
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self.current = 0.0
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self.voltage = 0.0
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if __name__ == "__main__":
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service = Device()
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Server(service).run()
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```
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In the above example, we define a Device class that extends DataService. We define a few properties (current, voltage, power) and their getter and setter methods.
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### Running the Server
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Once your DataService is defined, you can create an instance of it and run the server:
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```python
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from pydase import Server
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# ... defining the Device class ...
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if __name__ == "__main__":
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service = Device()
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Server(service).run()
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```
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This will start the server, making your Device service accessible via RPC and a web server at http://localhost:8001.
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### Accessing the Web Interface
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Once the server is running, you can access the web interface in a browser:
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In this interface, you can interact with the properties of your `Device` service.
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### Connecting to the Service using rpyc
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You can also connect to the service using `rpyc`. Here's an example on how to establish a connection and interact with the service:
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```python
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import rpyc
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# Connect to the service
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conn = rpyc.connect("<ip_addr>", 18871)
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client = conn.root
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# Interact with the service
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client.voltage = 5.0
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print(client.voltage) # prints 5.0
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```
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In this example, replace `<ip_addr>` with the IP address of the machine where the service is running. After establishing a connection, you can interact with the service attributes as if they were local attributes.
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<!--usage-end-->
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## Understanding the Component System
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In `pydase`, components are fundamental building blocks that bridge the Python backend logic with frontend visual representation and interactions. This system can be understood based on the following categories:
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### Built-in Type and Enum Components
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`pydase` automatically maps standard Python data types to their corresponding frontend components:
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- `str`: Translated into a `StringComponent` on the frontend.
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- `int` and `float`: Manifested as the `NumberComponent`.
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- `bool`: Rendered as a `ButtonComponent`.
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- `list`: Each item displayed individually, named after the list attribute and its index.
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- `enum.Enum`: Presented as an `EnumComponent`, facilitating dropdown selection.
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### Method Components
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Methods within the `DataService` class have frontend representations:
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- Regular Methods: These are rendered as a `MethodComponent` in the frontend, allowing users to execute the method via an "execute" button.
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- Asynchronous Methods: These are manifested as the `AsyncMethodComponent` with "start"/"stop" buttons to manage the execution of [tasks](#understanding-tasks-in-pydase).
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### DataService Instances (Nested Classes)
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Nested `DataService` instances offer an organized hierarchy for components, enabling richer applications. Each nested class might have its own attributes and methods, each mapped to a frontend component.
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Here is an example:
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```python
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from pydase import DataService, Server
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class Channel(DataService):
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def __init__(self, channel_id: int) -> None:
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self._channel_id = channel_id
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self._current = 0.0
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super().__init__()
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@property
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def current(self) -> float:
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# run code to get current
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result = self._current
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return result
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@current.setter
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def current(self, value: float) -> None:
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# run code to set current
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self._current = value
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class Device(DataService):
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def __init__(self) -> None:
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self.channels = [Channel(i) for i in range(2)]
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super().__init__()
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if __name__ == "__main__":
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service = Device()
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Server(service).run()
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```
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**Note** that defining classes within `DataService` classes is not supported (see [this issue](https://github.com/tiqi-group/pydase/issues/16)).
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### Custom Components (`pydase.components`)
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The custom components in `pydase` have two main parts:
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- A **Python Component Class** in the backend, implementing the logic needed to set, update, and manage the component's state and data.
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- A **Frontend React Component** that renders and manages user interaction in the browser.
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Below are the components available in the `pydase.components` module, accompanied by their Python usage:
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- `Image`: This component allows users to display and update images within the application.
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```python
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import matplotlib.pyplot as plt
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import numpy as np
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import pydase
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from pydase.components.image import Image
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class MyDataService(pydase.DataService):
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my_image = Image()
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if __name__ == "__main__":
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service = MyDataService()
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# loading from local path
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service.my_image.load_from_path("/your/image/path/")
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# loading from a URL
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service.my_image.load_from_url("https://cataas.com/cat")
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# loading a matplotlib figure
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fig = plt.figure()
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x = np.linspace(0, 2 * np.pi)
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plt.plot(x, np.sin(x))
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plt.grid()
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service.my_image.load_from_matplotlib_figure(fig)
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pydase.Server(service).run()
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```
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- `NumberSlider`: An interactive slider component to adjust numerical values, including floats and integers, on the frontend while synchronizing the data with the backend in real-time.
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```python
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import pydase
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from pydase.components import NumberSlider
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class MyService(pydase.DataService):
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slider = NumberSlider(value=3.5, min=0, max=10, step_size=0.1)
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if __name__ == "__main__":
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service = MyService()
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pydase.Server(service).run()
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```
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#### Extending with New Components
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Users can also extend the library by creating custom components. This involves defining the behavior on the Python backend and the visual representation on the frontend. For those looking to introduce new components, the [guide on adding components](https://pydase.readthedocs.io/en/latest/dev-guide/Adding_Components/) provides detailed steps on achieving this.
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## Understanding Service Persistence
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`pydase` allows you to easily persist the state of your service by saving it to a file. This is especially useful when you want to maintain the service's state across different runs.
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To save the state of your service, pass a `filename` keyword argument to the `__init__` method of the `DataService` base class. If the file specified by `filename` does not exist, the service will create this file and store its state in it when the service is shut down. If the file already exists, the service will load the state from this file, setting the values of its attributes to the values stored in the file.
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Here's an example:
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```python
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from pydase import DataService, Server
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class Device(DataService):
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def __init__(self, filename: str) -> None:
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# ... your init code ...
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# Pass the filename argument to the parent class
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super().__init__(filename=filename)
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# ... defining the Device class ...
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if __name__ == "__main__":
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service = Device("device_state.json")
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Server(service).run()
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```
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In this example, the state of the `Device` service will be saved to `device_state.json` when the service is shut down. If `device_state.json` exists when the service is started, the service will restore its state from this file.
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Note: If the service class structure has changed since the last time its state was saved, only the attributes that have remained the same will be restored from the settings file.
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## Understanding Tasks in pydase
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In `pydase`, a task is defined as an asynchronous function contained in a class that inherits from `DataService`. These tasks usually contain a while loop and are designed to carry out periodic functions.
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For example, a task might be used to periodically read sensor data, update a database, or perform any other recurring job. The core feature of `pydase` is its ability to automatically generate start and stop functions for these tasks. This allows you to control task execution via both the frontend and an `rpyc` client, giving you flexible and powerful control over your service's operation.
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Another powerful feature of `pydase` is its ability to automatically start tasks upon initialization of the service. By specifying the tasks and their arguments in the `_autostart_tasks` dictionary in your service class's `__init__` method, `pydase` will automatically start these tasks when the server is started. Here's an example:
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```python
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from pydase import DataService, Server
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class SensorService(DataService):
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def __init__(self):
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self.readout_frequency = 1.0
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self._autostart_tasks = {"read_sensor_data": ()} # args passed to the function go there
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super().__init__()
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def _process_data(self, data: ...) -> None:
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...
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def _read_from_sensor(self) -> Any:
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...
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async def read_sensor_data(self):
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while True:
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data = self._read_from_sensor()
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self._process_data(data) # Process the data as needed
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await asyncio.sleep(self.readout_frequency)
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if __name__ == "__main__":
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service = SensorService()
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Server(service).run()
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```
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In this example, `read_sensor_data` is a task that continuously reads data from a sensor. The readout frequency can be updated using the `readout_frequency` attribute.
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By listing it in the `_autostart_tasks` dictionary, it will automatically start running when `Server(service).run()` is executed.
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As with all tasks, `pydase` will also generate `start_read_sensor_data` and `stop_read_sensor_data` methods, which can be called to manually start and stop the data reading task.
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## Understanding Units in pydase
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`pydase` integrates with the [`pint`](https://pint.readthedocs.io/en/stable/) package to allow you to work with physical quantities within your service. This enables you to define attributes with units, making your service more expressive and ensuring consistency in the handling of physical quantities.
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You can define quantities in your `DataService` subclass using `pydase`'s `units` functionality. These quantities can be set and accessed like regular attributes, and `pydase` will automatically handle the conversion between floats and quantities with units.
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Here's an example:
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```python
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from typing import Any
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from pydase import DataService, Server
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import pydase.units as u
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class ServiceClass(DataService):
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voltage = 1.0 * u.units.V
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_current: u.Quantity = 1.0 * u.units.mA
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@property
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def current(self) -> u.Quantity:
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return self._current
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@current.setter
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def current(self, value: Any) -> None:
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self._current = value
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if __name__ == "__main__":
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service = ServiceClass()
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# You can just set floats to the Quantity objects. The DataService __setattr__ will
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# automatically convert this
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service.voltage = 10.0
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service.current = 1.5
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Server(service).run()
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```
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In the frontend, quantities are rendered as floats, with the unit displayed as additional text. This allows you to maintain a clear and consistent representation of physical quantities across both the backend and frontend of your service.
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Should you need to access the magnitude or the unit of a quantity, you can use the `.m` attribute or the `.u` attribute of the variable, respectively. For example, this could be necessary to set the periodicity of a task:
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```python
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import asyncio
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from pydase import DataService, Server
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import pydase.units as u
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class ServiceClass(DataService):
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readout_wait_time = 1.0 * u.units.ms
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async def read_sensor_data(self):
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while True:
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print("Reading out sensor ...")
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await asyncio.sleep(self.readout_wait_time.to("s").m)
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if __name__ == "__main__":
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service = ServiceClass()
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Server(service).run()
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```
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For more information about what you can do with the units, please consult the documentation of [`pint`](https://pint.readthedocs.io/en/stable/).
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## Changing the Log Level
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You can change the log level of loguru by either
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1. (RECOMMENDED) setting the `ENVIRONMENT` environment variable to "production" or "development"
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```bash
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ENVIRONMENT="production" python -m <module_using_pydase>
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```
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The production environment will only log messages above "INFO", the development environment (default) logs everything above "DEBUG".
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2. calling the `pydase.utils.logging.setup_logging` function with the desired log level
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```python
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# <your_script.py>
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from pydase.utils.logging import setup_logging
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setup_logging("INFO")
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```
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## Documentation
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The full documentation provides more detailed information about `pydase`, including advanced usage examples, API references, and tips for troubleshooting common issues. See the [full documentation](https://pydase.readthedocs.io/en/latest/) for more information.
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## Contributing
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We welcome contributions! Please see [contributing.md](https://pydase.readthedocs.io/en/latest/about/contributing/) for details on how to contribute.
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## License
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`pydase` is licensed under the [MIT License](https://github.com/tiqi-group/pydase/blob/main/LICENSE).
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