A minor rewrite of the NodeJS EventEmitter in Python
Project description
node_events.py
A minor rewrite of the NodeJS EventEmitter in Python
Installing
Via PyPI:
pip install node_events
Usage
from node_events import EventEmitter
myEmitter = EventEmitter()
def fn():
print("An event occurred")
myEmitter.on('event', fn)
myEmitter.emit('event')
# Prints
# An event occurred
API
Class: EventEmitter
The EventEmitter
class is defined and exposed publicly by the module:
from node_events import EventEmitter
EventEmitter.addListener
(eventName, listener)
eventName
: <string>listener
: <function>- Returns: <EventEmitter>
Alias for self.on(eventName, listener)
EventEmitter.on
(eventName, listener)
eventName
: <string> The name of the event.listener
: <function> The callback function.- Returns: <EventEmitter>
Appends the listener
to the listeners array for the event named eventName
. Multiple calls passing the same combination of eventName and listener will result in the listener being added, and called, multiple times.
By default, event listeners are invoked in the order they are added. The emitter.prependListener()
method can be used as an alternative to add the event listener to the beginning of the listeners array.
Returns a reference to the EventEmitter
, so that calls can be chained.
emitter = EventEmitter()
def appendListener():
print('a')
def prependListener():
print('b')
emitter.on('test', appendListener)
emitter.prependListener('test', appendListener)
emitter.emit('test')
# Prints
# b
# a
EventEmitter.once
(eventName, listener)
eventName
: <string> The name of the event.listener
: <function> The callback function.- Returns: <EventEmitter>
Adds a one-time listener
function for the event named eventName
. The next time eventName
is triggered, this listener is removed and then invoked.
By default, event listeners are invoked in the order they are added. The emitter.prependOnceListener()
method can be used as an alternative to add the event listener to the beginning of the listeners array.
Returns a reference to the EventEmitter
, so that calls can be chained.
emitter = EventEmitter()
def appendListener():
print('a')
def prependListener():
print('b')
emitter.once('test', appendListener)
emitter.prependOnceListener('test', appendListener)
emitter.emit('test')
# Prints
# b
# a
EventEmitter.prependListener
(eventName, listener)
eventName
: <string> The name of the event.listener
: <function> The callback function.- Returns: <EventEmitter>
Adds the listener
function to the beginning of the listeners array for the event named eventName
. Multiple calls passing the same combination of eventName and listener will result in the listener being added, and called, multiple times.
emitter = EventEmitter()
def newConnection():
print('someone connected!')
emitter.prependListener('connection', newConnection)
emitter.emit('connection')
Returns a reference to the EventEmitter
, so that calls can be chained.
EventEmitter.prependOnceListener
(eventName, listener)
eventName
: <string> The name of the event.listener
: <function> The callback function.- Returns: <EventEmitter>
Adds a one-time listener
function for the event named eventName
to the beginning of the listeners array. The next time eventName
is triggered, this listener is removed, and then invoked.
emitter = EventEmitter()
def newConnection():
print('someone connected!')
emitter.prependOnceListener('connection', newConnection)
emitter.emit('connection')
Returns a reference to the EventEmitter
, so that calls can be chained.
EventEmitter.removeAllListeners
([eventName])
eventName
: <string> The name of the event.- Returns: <EventEmitter>
Removes all listeners, or those of the specified eventName
.
Returns a reference to the EventEmitter, so that calls can be chained.
EventEmitter.removeListener
(eventName, listener)
eventName
: <string>listener
: <function>- Returns: <EventEmitter>
Removes the specified listener
from the listener array for the event named eventName
.
EventEmitter.hasEvent
(eventName, raiseException)
eventName
: <string>raiseException
: <boolean> (Default:False
)- Returns: <EventEmitter>
Check if the event emitter has within itself an event named eventName
, return a boolean for the operation.
if raiseException
is True, raise an exception if the result of the check evaluates to False
.
EventEmitter.hasListeners
(eventName)
eventName
: <string>raiseException
: <boolean>- Returns: <EventEmitter>
Safely check that the core EventListenerStack has at least one listener.
Implements the EventListenerStack::hasListeners()
inherently.
Class: EventListener
(listener)
listener
: <function>
This class wraps the listener
function with useful, sandboxed manipulative features
The EventListener
class is defined and exposed publicly by the module:
from node_events import EventListener
def fn():
print("test_fn")
EventListener(fn).respond()
# Prints
# test_fn
EventListener.listenerCount
(getter)
Number of times the function has been called
EventListener.respond
(*data)
*data
: <any>
Send the data
arguments to the encapsulated function in evaluation
EventListener.verify
(fn)
fn
: <function>- Returns: <boolean>
Check if fn
matches with the encapsulated function
Useful in finding the instance amongst others by matching its core
Class: EventListenerStack
(eventName)
eventName
: <string>
Stacking layer of listeners for an event defined named eventName
Serves as an interfacing remote for series of grouped listeners
The EventListenerStack
class is defined and exposed publicly by the module:
from node_events import EventListenerStack
def test_fn():
print("hi from test_fn")
stack = EventListenerStack("event_name")
stack.attachListener(test_fn, 0)
stack.respond()
# Print
# hi from test_fn
EventListenerStack.listeners
(getter)
Return a copy of the private listeners array. (recommended if iterations skips some indexes in self.rawListeners
)
EventListenerStack.listenerCount
(getter)
Return the number of listeners exist and are actively waiting for event firings
EventListenerStack.respond
(*data)
*data
: <any>- Returns: <boolean>
Send the data
arguments to all the listeners within the stack in the order of which they appear
Returns True if the stack has any active listeners who read the data else False
EventListenerStack.verifyHasListener
(fn)
fn
: <function>
Check if the stack has the listener fn
EventListenerStack.attachListener
(fn, index)
fn
: <function>index
: <number>
Attach the fn
listener to the event stack.
The index
parameter determines the index at which to place the function in the stack array
Note, function calls are based on orderly calls from the stack array
EventListenerStack.detachListener
(fn)
fn
: <function>- Returns: <boolean>
Detach the fn
listener from the stack if it exists returning True otherwise return False
EventListenerStack.detachAllListeners
()
Detach all the listeners within the stack
EventListenerStack.hasListeners
()
Check if the stack has any listeners within
EventListenerStack.extractInstanceOf
(fn)
fn
: <function>
Extract the EventListener
instance encapsulating the fn
listener if it exists otherwise return None
Development
Building
Feel free to clone, use in adherance to the license and perhaps send pull requests
git clone https://github.com/miraclx/node_events.py.git
cd node_events.py
# hack on code
python3 setup.py bdist_wheel
pip3 install dist/*.whl --user
License
Apache 2.0 © Miraculous Owonubi (@miraclx) <omiraculous@gmail.com>
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