To follow up on @jakevdp's answer, a completely equivalent but perhaps slightly more elegant way of systematically pre-empting this issue in equinox is to assign a value directly in the attribute definition:

class MyClass(eqx.Module):

    ...

    param: float = 0 # set to a placeholder to allow tracing
    
    def __init__(self):
        self.param = self._integral_moment(3)

    ...