DOMEventListener

Subscripe on DOM elements, trigger methods when they change

Notes

• Operates without a database by default
• can operate with whatever database you want

Usage

Example: Subscribing on the stackoverflow feed:

from domeventlistener.listen import Listener


# your event handler
def event_handler(event_type, data):
    print(event_type, data)


listener = Listener(
    'https://stackoverflow.com/questions',
    '#mainbar',
    event_handler
)

# mount it on the element
listener.mount()

try:
    listener.run()
except KeyboardInterrupt():
    quit()

For example, when the DOM has changed the event_handler defined will print
something like:

'changed', <unified diff between the new data and the old>

Changing where data is stored

By default, the element is stored in the RAM memory, you can change this
by setting read and write functions.

For example, if you want to use MongoDB:

from domeventlistener.listen import Listener
from myapp.mongo import db


def read_element():
    return str(db.collections.find_one({'name': 'element'})['element_str'])

def write_element(element_str):
    return db.collections.update_one(
        {'name': 'element', 'element_str': element_str},
        upsert=True
    )

...

listener = Listener(
    'https://stackoverflow.com/questions',
    '#mainbar',
    event_handler,
    read_element=read_element,
    write_element=write_element
)
...

Using with selenium + chromedriver

You can set the chrome attribute to use selenium webdriver:

...

mydriver = webdriver.Chrome(
    executable_path=config['chrome_driver'],
    chrome_options=chrome_options
)

listener = Listener(
    'https://stackoverflow.com/questions',
    '#mainbar',
    event_handler,
    read_element=read_element,
    write_element=write_element,
    chrome=mydriver # passing in my driver to use selenium + chromedriver
)
...

Pooling

Running multiple listeners at the same time:

from domeventlistener.listen import Listener
from domeventlistener.pool import ListenPool


# my event handler
def event_handler(event_type, data):
    print(event_type, data)


listener0 = Listener(
    domain='https://github.com/sebbekarlsson',
    query='a[title="Stars"]',
    event_handler=event_handler
)

pool = ListenPool()
 
# deploy as many listeners as you want.
# The "pool" will automaticaly start them once deployed using this method.
pool.deploy_listener(listener0) 

Using the domeventlistener in your application

from domeventlistener.listen import Listener


listener = Listener(
    domain='http://example.org',
    query='h1'
)

# boolean    string
has_changed, new_element_str = listener.poll_change()

Type of events

• changed - the DOM was changed
• emptied - the DOM is now empty / lost

CLI (Command line interface)

Installation

Install with pip:

pip install DOMEventListener

Install by cloning down:

git clone <this-project>
cd <this-project>
python setup.py install

Development

Unit testing

First install:

pip install pytest pytest-cov

Run the tests:

./test.sh

To run thests with chromedriver + selenium

echo '{"chromedriver": "/path/to/chromedriver"}' > domeventlistener/tests/config.json

License

License: gpl-3.0