Is __init__ the equivalent of a dataclass __post_init__? binding a value via a callable

Param
1

marketer_id is a callable that returns an ever-increasing number. I want to set the id of a new Marketer instance by calling marketer_id() when building the instance. I’m not sure if I can supply a callable as the default argument to a param and it will call it.

marketer_id = itertools.count()


class Marketer(Parameterized):
    id = Number()   # <--- how to bind to the result of invoking marketer_id()???
    sponsor = Marketer()
    front_line = Number(5)
2

The Number Parameter is a subclass of the Dynamic parameter type that accepts a callable, this is described in more details in this section of the user guide.

import itertools
import param

c = itertools.count()

class Marketer(param.Parameterized):
    id = param.Integer(lambda: next(c))

m = Marketer()
print(m.id, m.id, m.id)

image

3

But: we only want to give the object an id once at object construction time…

So a __post_init__ or __init__ method that binds id once is desired.

4

Oh ok. Then I guess this is one way to achieve this behavior.

import itertools
import param

c = itertools.count()

class Marketer(param.Parameterized):
    id = param.Integer(default=0, bounds=(0, None))

    def __init__(self, **params):
        super().__init__(**params)
        self.id = next(c)

m1 = Marketer()
print(m1.id)  # 0

m2 = Marketer()
print(m2.id) # 1