functools.partial objects cannot be used as `Dynamics.StateMachine.State` methods (onset, ongoing, etc.)

[Scott Mooney]

Creating a basic functools.partial object and assigning it to a State method, like:

def my_func(argument):
    print(argument)

sm.AddState("NewState", onset=partial(my_func, "new_state_onset"))

produces an error:

AttributeError: 'functools.partial' object has no attribute '__get__'

[Jeremy Hill]

I cannot replicate this with Shady 1.13.1 (git 79355e0 2020-12-02) on Python 3.7.3 for macOS 10.13 or on Python 3.7.6 for Windows 10.

In [1]: from Shady.Dynamics import StateMachine; sm = StateMachine(); from functools import partial

In [2]: paste
def my_func(argument):
    print(argument)

sm.AddState("NewState", onset=partial(my_func, "new_state_onset"))

## -- End pasted text --
Out[2]: <Shady.Dynamics.StateMachine.State at 0x10c347cf8>

In [3]: sm(0)
new_state_onset
Out[3]: <Shady.Dynamics.StateMachine.State at 0x10c347cf8>

Although it is true, on these Python versions, that the partial object has no __get__ :

In [4]: sm.current.onset
Out[4]: functools.partial(<function my_func at 0x10c2e8510>, 'new_state_onset')

In [5]: _.__get__
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-5-02173c58bbdf> in <module>
----> 1 _.__get__

AttributeError: 'functools.partial' object has no attribute '__get__'

In [6]:

So Shady 1.13.1 must be handling this contingency. I cannot replicate this problem even by rolling back to 1.8.x (early 2019). Double-check your python -m Shady --versions

‌

[Scott Mooney]

Clarification: it only happens when partial is used on a bound class method. My bad, I didn’t actually test the basic example I initially gave.

This does produce the error:

import Shady
from functools import partial


class MyClass:

    def __init__(self, message_prefix):
        self.message_prefix = message_prefix

    def flexible_onset(self, message):
        print(self.message_prefix + message)

    def add_to_state_machine(self, state_machine, state_name, message):
        state_machine.AddState(state_name, onset=partial(self.flexible_onset, message))


if __name__ == '__main__':
    c = MyClass("Prefix: ")
    sm = Shady.StateMachine()
    c.add_to_state_machine(sm, "MyState", "Suffix")
    sm.AddState("MyState2", onset=partial(c.flexible_onset, "Suffix"))  # ALSO ERROR

‌

[Jeremy Hill]

fixed in 654b50e (master branch)