Please see the code below. To summarize:

• Define one event
• Define two subscriber listening for the event above. Each subscriber has a listener method with the name on_event
• Each of the subscriber classes above defines an instance field, but with unique name (self.something in the first class, self.something2 in the second class)
• Define another class that posts an event

Run this scenario and get the error below:

Exception in thread thread-on_event:
Traceback (most recent call last):
  File "C:\Anaconda2\envs\python\lib\threading.py", line 801, in __bootstrap_inner
    self.run()
  File "C:\Anaconda2\envs\python\lib\site-packages\pyeventbus\pyeventbus.py", line 112, in run
    self.method(self.subscriber, self.event)
  File "C:/FractureID/projects/python/ui/spectraqc/PyEventBusBug.py", line 16, in on_event
    print (self.something)
AttributeError: Subscriber2 instance has no attribute 'something'

Exception in thread thread-on_event:
Traceback (most recent call last):
  File "C:\Anaconda2\envs\python\lib\threading.py", line 801, in __bootstrap_inner
    self.run()
  File "C:\Anaconda2\envs\python\lib\site-packages\pyeventbus\pyeventbus.py", line 112, in run
    self.method(self.subscriber, self.event)
  File "C:/FractureID/projects/python/ui/spectraqc/PyEventBusBug.py", line 26, in on_event
    print (self.something_else)
AttributeError: Subscriber1 instance has no attribute 'something_else'

It complains about the variable in class two not having the attribute in the first class and the other way around.

If I change on of the on_event to something else like on_event2 then the issue is gone.

from pyeventbus import *


class SomeEvent:
    def __init__(self):
        pass


class Subscriber1:
    def __init__(self):
        self.something = 'First subscriber'
        PyBus.Instance().register(self, self.__class__.__name__)

    @subscribe(threadMode=Mode.PARALLEL, onEvent=SomeEvent)
    def on_event(self, event):
        print (self.something)


class Subscriber2:
    def __init__(self):
        self.something_else = 'Second subscriber'
        PyBus.Instance().register(self, self.__class__.__name__)

    @subscribe(threadMode=Mode.PARALLEL, onEvent=SomeEvent)
    def on_event(self, event):
        print (self.something_else)


class PyEventBusBug:

    def __init__(self):
        Subscriber1()
        Subscriber2()
        PyBus.Instance().post(SomeEvent())


if __name__ == "__main__":
    PyEventBusBug()

  File "C:\Python27\lib\site-packages\pyeventbus\pyeventbus.py", line 116, in subscribe
    bus = PyBus.Instance()
  File "C:\Python27\lib\site-packages\pyeventbus\Singleton.py", line 30, in Instance
    self._instance = self._decorated()
  File "C:\Python27\lib\site-packages\pyeventbus\pyeventbus.py", line 24, in __init__
    for worker in [lambda: self.startWorkers() for i in range(self.num_threads)]: worker()
  File "C:\Python27\lib\site-packages\pyeventbus\pyeventbus.py", line 24, in <lambda>
    for worker in [lambda: self.startWorkers() for i in range(self.num_threads)]: worker()
  File "C:\Python27\lib\site-packages\pyeventbus\pyeventbus.py", line 30, in startWorkers
    worker.start()
  File "C:\Python27\lib\threading.py", line 736, in start
    _start_new_thread(self.__bootstrap, ())
thread.error: can't start new thread

See also: https://stackoverflow.com/a/1835043/2583080