# Python Watchdog Module

The `watchdog` module provides an API and shell utilities to monitor file system events. It works cross-platform (Windows, Linux, macOS).

## Installation

```bash
pip install watchdog
```

## Importing the Module

```python
import time
from watchdog.observers import Observer
from watchdog.events import FileSystemEventHandler
```

## Event Handlers

To react to file system events, you need to create a subclass of `FileSystemEventHandler` and override the methods corresponding to the events you are interested in.

Common methods:
*   `on_any_event(event)`: Called for any event.
*   `on_created(event)`: Called when a file or directory is created.
*   `on_deleted(event)`: Called when a file or directory is deleted.
*   `on_modified(event)`: Called when a file or directory is modified.
*   `on_moved(event)`: Called when a file or directory is moved or renamed.

```python
class MyHandler(FileSystemEventHandler):
    def on_modified(self, event):
        print(f'File {event.src_path} has been modified')

    def on_created(self, event):
        print(f'File {event.src_path} has been created')
```

## The Observer

The `Observer` class monitors the file system and dispatches events to the event handler.

```python
if __name__ == "__main__":
    path = "."
    event_handler = MyHandler()
    observer = Observer()
    observer.schedule(event_handler, path, recursive=True)
    observer.start()
    
    try:
        while True:
            time.sleep(1)
    except KeyboardInterrupt:
        observer.stop()
    
    observer.join()
```

## Logging Example

Here is a complete example that logs all events to the console using the built-in `LoggingEventHandler`.

```python
import sys
import time
import logging
from watchdog.observers import Observer
from watchdog.events import LoggingEventHandler

if __name__ == "__main__":
    logging.basicConfig(level=logging.INFO,
                        format='%(asctime)s - %(message)s',
                        datefmt='%Y-%m-%d %H:%M:%S')
    
    path = sys.argv[1] if len(sys.argv) > 1 else '.'
    
    event_handler = LoggingEventHandler()
    observer = Observer()
    observer.schedule(event_handler, path, recursive=True)
    observer.start()
    
    try:
        while True:
            time.sleep(1)
    except KeyboardInterrupt:
        observer.stop()
    
    observer.join()
```

[[programming/python/python]]