Introduction to backcall

The backcall module in Python provides a simple yet powerful way to handle and manage callback functions, which are essential for asynchronous programming and event-driven applications. In this guide, we will explore multiple APIs provided by backcall with practical code examples to help you harness its full potential.

API Examples

1. callback

This decorator turns a regular function into a callback. The callback function can then be used in event handling systems.

 from backcall import callback
@callback def my_callback_function(arg):
    print(f'Callback received argument: {arg}')

2. CallbackHandler

This class manages multiple callbacks, providing methods to add, remove, and call callbacks.

 from backcall import CallbackHandler
handler = CallbackHandler()
@handler.add def another_callback(arg):
    print(f'Handling argument: {arg}')

handler.call('Test Argument')  # Outputs: Handling argument: Test Argument 

3. CallbackHook

This class provides more versatile hook capabilities than simple function decorators.

 from backcall import CallbackHook
hook = CallbackHook()
def pre_hook(arg):
    print(f'Pre-hook: {arg}')
    
def post_hook(arg):
    print(f'Post-hook: {arg}')

hook.add_pre(pre_hook) hook.add_post(post_hook)
@hook def target_function(arg):
    print(f'Target function: {arg}')

target_function('Executing Hook')   # Outputs: # Pre-hook: Executing Hook # Target function: Executing Hook # Post-hook: Executing Hook 

Application Example

Let’s create a simple app that demonstrates the usage of multiple backcall APIs for managing user actions in a GUI application.

 from backcall import callback, CallbackHandler, CallbackHook
handler = CallbackHandler() hook = CallbackHook()
@hook @callback def button_click(event):
    print(f'Button clicked: {event}')

@handler.add def log_event(event):
    print(f'Logging: {event}')

hook.add_post(lambda e: print(f'Post action: {e}'))
# Simulate button click event event = 'User clicked the button' button_click(event) handler.call(event) 

Conclusion

With the backcall module, you can easily manage callback functions and ensure your asynchronous code is well-organized and efficient. Whether you’re developing GUIs, handling network events, or creating comprehensive hooks, backcall provides the tools to streamline your process.

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