fastwire

Fastwire is a simple package to facilitate communication between objects. It provides similar functionality to several other packages, such as:

• blinker
• wires
• wired
• observable
• pyDispatcher
• pymitter
• py-notify
• zope-event

Fastwire is intended to be elegant to use, fast to implement, and more flexible, while maintianing high performance.

Basic usage

Create a signal container:

import fastwire as fw

sc = fw.SignalContainer()

Then create a signal...

signal = sc.signal('your_name')

We can connect to that signal like this:

class A():
    def __init__(self):
        signal.connect(self.connected)

    def connected(self, a):
        print('Class A instance received a: ' + str(a))

a = B()
signal.connect(a.connected)	
signal.emit(a=5.7)
# Class A instance received a 5.7

And we can connect other signals if we want to:

signal_b = sc.signal('new_sig')
signal_b.connect(a.connected)
signal_b.emit(a=3)
# Class A instance received a 3

Connecting also works with functions. We can connect a function to the same signal.

def test_fun(a):
    print('test_fun got a ' + str(a))
    
signal.connect(test_fun)
signal.emit(a=5.7)
# Class A instance received a 5.7
# test_fun got a 5.7

Only keyword arguments are accepted to ensure the required type of data is passed.

The emit method doesn't return anything. But the signal.fetch method does. It requires there to be a single function or method that 'supplies' the return value. The signal.fetch_all method returns a list of return values from all receivers.

Signal properties

signal.n

Number of recievers.

signal.receivers_present

True if receivers are present.

name

The name of the signal.

Decorators

It can be convenient to use decorators to automatically connect. Do do this, the class needs to inherit fw.Wired.

signal_c = sc.signal('C')

class B(fw.Wired):
	@fw.receives(signal_c)
	def connected(self, a):
		print('Class B instance got ' + str(a))

b = B()
signal_c.emit(a=7)
# Class B instance got 7

Functions need to use a different decorator.

@fw.fn_receives(signal_c)
def test_fun_2(a):
    print('test_fun_2 got ' + str(a))
signal_c.emit(a=88)
# Class B instance got 88
# test_fun_2 got 88

Use the @fastwire.supply decorator for methods that supply data, and the @fastwire.fn_supply decorator for functions that supply data.

Conditions

Conditions can be added. They need to have a method called 'check', which is passed combined keyword arguments from the caller and receiver. It needs to return a boolean. If it's true, the given receiver gets the signal, if not, it doesn't. They also need a class attribute called 'name'.

Add a signal condition like this:

class My_Condition():
    name = 'default'
    def check(self, a, **kwargs):
        ''' The main check call - must return a boolean '''
        if a < 10:
            return True
        else:
            return False
            
signal.add_condition(My_Condition())

Now, receivers only get the signal when a is less than 10:

signal.emit(a=5.7)
# Class A instance received a 5.7
# test_fun got a 5.7

signal.emit(a=15)
# Nothing happens

To remove:

signal.remove_condition(My_Condition.name)
signal.emit(a=15)
# Class A instance received a 15
# test_fun got a 15

Condition classes are completely open - they can be as simple as the above example or as complex as a state machine.

Muting

No receivers get a muted signal. You can mute and unmute a signal easily...

signal.mute()
signal.emit(a=3)
# Nothing mappens

signal.unmute()
signal.emit(a=3)
# Class A instance received a 3
# test_fun got a 3

Documentation

Documentation is hosted at ReadTheDocs.org.

https://fastwire.readthedocs.io/en/latest/