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basic.py
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basic.py
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"""
Demonstrates a simple event emmiter
"""
class EventEmiiter:
def __init__(self):
# initialize empty event map
self.__eventMap = {}
def on(self, name, target):
"""Appends the target function in array against name key in __eventMap dict
"""
targets = self.__eventMap.get(name, [])
targets.append(target)
self.__eventMap[name] = targets
def emit(self, name, *args):
"""Calls all the target functions in array against name key in __eventMap dict
"""
for e in self.__eventMap.get(name, []):
callable(e) and e(*args)
def remove_all_listeners(self, name):
"""Removes name key in __eventMap dict
"""
self.__eventMap.pop(name, '')
def remove_listener(self, name, target):
"""Removes specific target function for a given name key in __eventMap dict
"""
list = []
for e in self.__eventMap.get(name, []):
if e is not target:
list.append(e)
self.__eventMap[name] = list
def off(self, name, target):
"""Alias for remove_listener
"""
self.remove_listener(name, target)
def listeners(self, name):
"""Returns all the listeners currently registered for an event
"""
return self.__eventMap.get(name, [])
def listener_count(self, name):
"""Returns count of the listeners currently registered for an event
"""
return len(self.listeners(name))
def event_names(self):
"""Returns all the event names set currently registered
"""
return self.__eventMap.keys()
# ------------------------------------------------------------------------
def on_some_event_occured(*args):
print('on event emitted', args)
def result(*args):
print('computation_result from result()', args[0])
def add_numbers(emitter, *args):
sum = 0
for n in args:
sum += n
# both target functions result() and some_other_result_listener()
# will recieve the computation_result event
emitter.emit('computation_result', sum)
def main():
emitter = EventEmiiter()
# registering events
# eventA is registered 3 times
emitter.on('eventA', on_some_event_occured)
emitter.on('eventA', on_some_event_occured)
emitter.on('eventA', on_some_event_occured)
# eventB is registered 1 time
emitter.on('eventB', on_some_event_occured)
# events now emitted with arguments
# eventA when emitted will result in the target function on_event_a() called thrice
emitter.emit('eventA', 'eventA', 'data1', 'data2')
# eventB when emitted will result in the target function on_event_b() called once
emitter.emit('eventB')
# a more practical illustration is below
# computation_result is registered for 2 different target functions
emitter.on('computation_result', result)
emitter.on('computation_result', on_some_event_occured)
# add_numbers is passed on the emitter to emit event upon computation completion
add_numbers(emitter, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
# emitter removes all listeners for eventA
emitter.remove_all_listeners('eventA')
# since no target is registered, below emit has not effect on any target function
emitter.emit('eventA')
# unregister target on_some_event_occured() for event 'computation_result
emitter.off('computation_result', on_some_event_occured)
# call add_numbers() again now results in 'computation_result' emit only to result() target
add_numbers(emitter, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
if __name__ == '__main__':
main()