How to pass data in the case of inheriting from the Machine class?

[vba34520]

Install

pip install  transitions==1.16.0

It's okay.

from transitions import Machine


class Matter(object):
    def __init__(self):
        self.temp = 0

    def set_environment(self, event):
        self.temp = event.kwargs.get('temp', 0)

    def print_pressure(self):
        print(self.temp)


lump = Matter()
machine = Machine(lump, ['solid', 'liquid'], send_event=True, initial='solid')
machine.add_transition('melt', 'solid', 'liquid', before='set_environment')
lump.melt(temp=45)
lump.print_pressure()  # 45

I want to pass data in the case of inheriting from the Machine class like this, but it doesn't work. Thanks!

from transitions import Machine


class Matter(Machine):
    def __init__(self):
        self.temp = 0
        states = ['solid', 'liquid', 'gas']
        Machine.__init__(self, states=states, send_event=True, initial='solid')
        self.add_transition('melt', 'solid', 'liquid')

    def set_environment(self, event):
        self.temp = event.kwargs.get('temp', 0)

    def print_pressure(self):
        print(self.temp)


lump = Matter()
lump.melt(temp=45)
lump.print_pressure()  # 0

[aleneum]

Hello @vba34520,

pip install transitions==1.16.0

this looks incorrect. The current version of transitions is 0.9.0

In the second example you do not execute the callback set_environment. Compare

machine.add_transition('melt', 'solid', 'liquid', before='set_environment')

with

self.add_transition('melt', 'solid', 'liquid')

If you change this to

self.add_transition('melt', 'solid', 'liquid', before='set_environment')

you will get your desired output.