Python3 class refactor

I wrote some python3 code a long time ago and it’s very ugly. It has a lot of boilerplate and definitely can be improved. I need advice on how to make it better. please take a look

def _safe_value(value, default, reject=None):
    return value if value is not reject else default


# Bullet class
class Bullet(GameParticle):
    def __init__(self, x, y, angle, speed=None, rad=None, weapon=None,
                 color=None, hp=1.0, dmg=1.0, lifespan=60 * 4):
        if isinstance(weapon, WeaponType):
            speed = _safe_value(speed, weapon.speed)
            rad = _safe_value(rad, weapon.rad)
            hp = _safe_value(hp, weapon.hp, 1.0)
            dmg = _safe_value(dmg, weapon.dmg, 1.0)
            color = _safe_value(color, weapon.color)
        speed = _safe_value(speed, 0.0)
        rad = _safe_value(rad, BULLET_RADIUS)
        color = _safe_value(color, BULLET_COLOR)
        super().__init__(x, y, angle, speed, rad, color, hp, dmg)
        self.lifespan = lifespan

Details

• None is used to indicate unspecified value.
• I did not register a float value as “unspecified” because it may be
  used.
• I dont want to change the function params because it’s already in
  use.

Difficulties

• when __init__ is called, sometimes it’s with a WeaponType, sometimes it’s not
• when WeaponType is specified, other params such as speed may still be specified and we need to follow the specified speed instead
• I tried to create a general function that filters the values but then ill need to use getattr(weapon, varname) which is even worse

Goal

• call _safe_value only once for each argument
• if possible remove the mumbo jumbo from the __init__