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cs-events-0.4.1
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C#-style event handling mechanism for Python
| ویژگی | مقدار |
|---|---|
| سیستم عامل | - |
| نام فایل | cs-events-0.4.1 |
| نام | cs-events |
| نسخه کتابخانه | 0.4.1 |
| نگهدارنده | [] |
| ایمیل نگهدارنده | [] |
| نویسنده | Daniel Jeong |
| ایمیل نویسنده | wise0704@outlook.com |
| آدرس صفحه اصلی | https://github.com/wise0704/python-cs-events |
| آدرس اینترنتی | https://pypi.org/project/cs-events/ |
| مجوز | MIT |
# C#-Style Event Handling Mechanism for Python
<p align="center">
<a href="https://pypi.org/project/cs-events/">
<img alt="pypi"
src="https://img.shields.io/pypi/v/cs-events?logo=pypi&logoColor=EEE" /></a>
<a href="https://pypi.org/project/cs-events/">
<img alt="status"
src="https://img.shields.io/pypi/status/cs-events" /></a>
<a href="https://pypistats.org/packages/cs-events">
<img alt="downloads"
src="https://img.shields.io/pypi/dm/cs-events" /></a>
<a href="https://www.python.org/downloads/">
<img alt="python"
src="https://img.shields.io/pypi/pyversions/cs-events?logo=python&logoColor=yellow" /></a>
<a href="https://github.com/wise0704/python-cs-events/blob/master/LICENSE">
<img alt="license"
src="https://img.shields.io/pypi/l/cs-events?logo=data:image/svg+xml;base64,PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIGZpbGw9Im5vbmUiIHZpZXdCb3g9IjAgMCAyNCAyNCIgc3Ryb2tlPSIjRkZGIj48cGF0aCBzdHJva2UtbGluZWNhcD0icm91bmQiIHN0cm9rZS1saW5lam9pbj0icm91bmQiIHN0cm9rZS13aWR0aD0iMiIgZD0ibTMgNiAzIDFtMCAwLTMgOWE1LjAwMiA1LjAwMiAwIDAgMCA2LjAwMSAwTTYgN2wzIDlNNiA3bDYtMm02IDIgMy0xbS0zIDEtMyA5YTUuMDAyIDUuMDAyIDAgMCAwIDYuMDAxIDBNMTggN2wzIDltLTMtOS02LTJtMC0ydjJtMCAxNlY1bTAgMTZIOW0zIDBoMyIvPjwvc3ZnPg==" /></a>
<br/>
<a href="https://github.com/wise0704/python-cs-events/actions/workflows/python-package.yml">
<img alt="build"
src="https://img.shields.io/github/actions/workflow/status/wise0704/python-cs-events/python-package.yml?logo=pytest" /></a>
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</p>
C# provides a very simple syntax using the [observer pattern](https://en.wikipedia.org/wiki/Observer_pattern) for its event handling system.
The aim of this project is to implement the pattern in python as similarly as possible.
In C#, an "event" is a field or a property of the delegate type `EventHandler`.
Since delegates in C# can be combined and removed with `+=` and `-=` operators,
event handlers can easily subscribe to or unsubscribe from the event using those operators.
Python does not support an addition of two `Callable` types.
So the `Event[**TArgs]` class is provided to mimic delegates:
```python
from events import Event
changed = Event[str, object]()
```
> C# naming convention prefers present/past participles (`changing`/`changed`) instead of `on`+infinitive (`on_change`) for events.
Handlers can subscribe to and unsubscribe from the event with the same syntax:
```python
def changed_handler(key: str, value: object) -> None:
...
changed += changed_handler
changed -= changed_handler
```
An event can be raised by simply invoking it with the arguments:
```python
changed("state", obj)
```
Since `Event` acts just like a delegate from C#, it is not required to be bound to a class or an instance object.
This is the major difference to other packages that try to implement the C#-style event system, which usually revolve around a container object for events.
An example class with event fields may look like this:
```python
class EventExample:
def __init__(self) -> None:
self.updated: Event[str] = Event()
self.__value: str = ""
def update(self, value: str) -> None:
if self.__value != value:
self.__value = value
self.updated(value)
obj = EventExample()
obj.updated += lambda value: print(f"obj.{value=}")
obj.update("new value")
```
A class decorator `@events` is provided as a shortcut for event fields:
```python
from events import Event, events
@events
class EventFieldsExample:
item_added: Event[object]
item_removed: Event[object]
item_updated: Event[object, str]
```
C# also provides event properties with `add` and `remove` accessors:
```C#
public event EventHandler<T> Changed
{
add { ... }
remove { ... }
}
```
This feature is useful for classes that do not actually own the events, but need to forward the subscriptions to the underlying object that do own the events.
The `@event[**TArgs]` decorator and the `accessors[**TArgs]` type are provided to support this feature:
```python
from events import accessors, event, EventHandler
class EventPropertyExample:
@event[str, object]
def changed() -> accessors[str, object]:
def add(self: Self, value: EventHandler[str, object]) -> None:
...
def remove(self: Self, value: EventHandler[str, object]) -> None:
...
return (add, remove)
```
Furthermore, the `EventHandlerCollection` interface is provided to support the functionalities of `System.ComponentModel.EventHandlerList` class from C#, along with the two implementations `EventHandlerList` and `EventHandlerDict` using a linked list and a dictionary respectively. The behaviour of `EventHandlerList` is exactly the same as of its counterpart from C#.
A typical usage of `EventHandlerList` in C# can be translated directly into the python code:
```python
class EventPropertyExample:
__event_changed: Final = object()
@event # [str, object] is inferred
def changed(): # -> accessors[str, object] is inferred
def add(self: Self, value: EventHandler[str, object]) -> None:
self.__events.add_handler(self.__event_changed, value)
def remove(self: Self, value: EventHandler[str, object]) -> None:
self.__events.remove_handler(self.__event_changed, value)
return (add, remove)
def __init__(self) -> None:
self.__events = EventHandlerList()
def perform_change(self, key: str, value: object) -> None:
handler = self.__events[self.__event_changed]
if handler:
handler(key, value)
```
The class decorator `@events` also provides a shortcut for event properties.
The above code can be shortened to:
```python
@events(collection="__events")
class EventPropertyExample:
changed: event[str, object]
def __init__(self) -> None:
self.__events = EventHandlerList()
def perform_change(self, key: str, value: object) -> None:
self.__events.invoke("changed", key, value)
```
## Installation
Install using [`pip`](https://pypi.org/project/pip/):
```console
pip install cs-events
```
نیازمندی
| مقدار | نام |
|---|---|
| >=4.0.1,<5.0.0 | typing-extensions |
زبان مورد نیاز
| مقدار | نام |
|---|---|
| >=3.10,<4.0 | Python |
نحوه نصب
نصب پکیج whl cs-events-0.4.1:
pip install cs-events-0.4.1.whl
نصب پکیج tar.gz cs-events-0.4.1:
pip install cs-events-0.4.1.tar.gz