Can't figure out how to implement event system. I am doing project with tkinter. And I need to use events. How to have events like Java or C# events?
I searched a lot but can't figure out the right way.
Here is the event class I am trying to implement.
class Event(object):
def __init__(self):
self.handlers = []
def add(self, handler):
self.handlers.append(handler)
return self
def remove(self, handler):
self.handlers.remove(handler)
return self
def fire(self, sender, earg=None):
for handler in self.handlers:
value = handler()
self.remove(handler)
return value
__iadd__ = add
__isub__ = remove
__call__ = fire
Here is Car class
class Car:
_speed = 0
events = Event()
def speed_up(self):
self._speed += 10
def speed_down(self):
self._speed -= 10
def get_speed(self):
return self._speed
And for last there is Window class (tkinter window)
class Window(tk.Tk):
def __init__(self):
super().__init__()
self.car = Car()
tk.Button(self, text="Speed Up", command=self.increase_speed).grid(sticky="nsew")
tk.Button(self, text="Speed Down", command=self.decrease_speed).grid(sticky="nsew")
self.speed_label = tk.Label(self, text="0")
self.speed_label.grid(sticky="nsew")
self.mainloop()
def increase_speed(self):
self.car
def decrease_speed(self):
pass
Here is tkinter window:
I want to accomplish: 1) On Speed Up button click "speed_up" should be added to events. 2) It should change value of self.speed_label. 3) It should be something like c# / Java events or c# delagetes.
Trying to learn this new concept to me. But having difficult time implementing this...
UPDATED! I was searching / editing and came up with a solution. Don't know if this solution is good. I will ask my teacher if this is a good way for implementing events. But for now the code look like this:
import tkinter as tk
class Observer():
_observers = []
def __init__(self):
self._observers.append(self)
self._observed_events = []
def observe(self, event_name, callback_fn):
self._observed_events.append({'event_name' : event_name, 'callback_fn' : callback_fn})
class Event():
def send(self, event_name, *callback_args):
for observer in Observer._observers:
for observable in observer._observed_events:
if observable['event_name'] == event_name:
observable['callback_fn'](*callback_args)
def receive(self, event_name, *callback_args):
for observer in Observer._observers:
for observable in observer._observed_events:
if observable['event_name'] == event_name:
response = observable['callback_fn'](*callback_args)
return response
class Car(Observer):
def __init__(self):
Observer.__init__(self)
self._current_speed = 0
def speed(self):
self._current_speed += 10
def slow(self):
self._current_speed -= 10
def current(self):
return self._current_speed
class Window(tk.Tk):
def __init__(self):
super().__init__()
self._car = Car()
self.store()
self.events = Event()
tk.Button(self, text="Speed Up", command=lambda:self.change_speed("speed")).grid(sticky="nsew")
tk.Button(self, text="Slow Down", command=lambda:self.change_speed("slow")).grid(sticky="nsew")
self.label = tk.Label(self, text=0)
self.label.grid()
self.settings()
def store(self):
self._car.observe("speed", self._car.speed)
self._car.observe("slow", self._car.slow)
self._car.observe("current", self._car.current)
def settings(self):
self.mainloop()
def change_speed(self, event):
self.events.send(event)
self.label.config(text=self.events.receive("current"))
Window()
