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Description:

blinker herald 0.2.0

Blinker Herald

The Blinker Herald includes helpers to easily emit signals using the excelent
blinker library.
Decorate a function or method with @blinker_herald.emit()
and pre and post signals will be automatically emitted to
all connected handlers.

Free software: ISC license
Documentation: https://blinker_herald.readthedocs.org.

Features

All the features provided by blinker
+ an easy decorator @emit() to magically emit signals when your functions are called and before it returns a result.
A signals namespace proxy to discover the signals in your project
Customizable for your needs

Usage
Let’s say you have a class and wants to emit a signal for a specific method:
from blinker_herald import emit

class SomeClass(object):

@emit()
def do_something(self, arg1):
# here is were magically the 'pre' signal will be sent
return 'something done'
# here is were magically the 'post' signal will be sent
using @emit decorator makes blinker_herald to emit a signal for that method
and now you can connect handlers to capture that signals
You can capture pre signal to manipulate the object:
SomeClass.do_something.pre.connect
def handle_pre(sender, signal_emitter, **kwargs):
signal_emitter.foo = 'bar'
signal_emitter.do_another_thing()
And you can also capture the post signal to log the results:
SomeClass.do_something.post.connect
def handle_post(sender, signal_emitter, result, **kwargs):
logger.info("The method {0} returned {1}".format(sender, result))
You can also use the namespace proxy blinker_herald.signals to connect
handlers to signals, the signal name is the prefix pre or post
followed by _ and the method name:
from blinker_herald import signals

@signals.pre_do_something.connect
def handle_pre(sender, signal_emitter, **kwargs):
...
If you have a lot of subclasses emitting signals with the same name and you
need to capture only specific signals, you can specify that you want to listen
to only one type of sender:
from blinker_herald import emit, signals, SENDER_CLASS
class BaseModel(object):
...
@emit(sender=SENDER_CLASS)
def create(self, **kwargs):
new_instance = my_project.new(self, **kwargs)
return new_instance

class One(BaseModel):
pass

class Two(BaseModel):
pass

Note
By default the sender is always the instance but you can use SENDER_CLASS
to force the sender to be the class another options are SENDER_CLASS_NAME,
SENDER_MODULE, SENDER_NAME and you can also pass a string, an object
or a lambda receiving the sender instance e.g: @emit(sender=lambda self: self.get_sender())

Using SENDER_CLASS you can now connect to specific signal:
from blinker_herald import signals

@signals.post_create.connect_via(One)
def handle_post_only_for_one(sender, signal_emitter, result, **kwargs):
# sender is the class One (cls)
# signal the instance of the class One (self)
# result is the return of the method create
The above will handle the create method signal for the class One but not for the class Two
You can also be more specific about the signal you want to connect using the
__ double underscore to provide method name:
from blinker_herald import signals

@signals.module_name__ClassName__post_method_name.connect
def handle_post(sender, signal_emitter, result, **kwargs):
...
The above will connect to the post signal emitted by module_name.ClassName.method_name

Note
You don’t have to use the pattern above if your project do not have a lot of
method name collisions, using only the method name will be just fine for most cases.

Credits
This software was first created by SatelliteQE team to provide signals to
Robottelo and Nailgun

History
0.1.0 (2016-05-28)

First release on PyPI.