用相同的名称添加类内实例的所有变量

Question

I have a class named Robot , which creates a number of instances of the classes Segment and Pointmass . All these instances have a variable mass . How can I obtain the total mass of all the objects within the object with the same variable name mass ?

What I do right now:

class Robot:
    def __init__(self, massJoint1, massJoint2, massJoint3, massSlide, reachSlide, massArm, lengthArm):
        self.joint1 = Pointmass(massJoint1)
        self.joint2 = Pointmass(massJoint2)
        self.joint3 = Pointmass(massJoint3)

        self.slide = Slide(massSlide, reachSlide)
        self.arm = Arm(massArm, lengthArm)

        self.totalmass = self.joint1.mass + self.joint2.mass + self.joint3.mass + self.slide.mass + self.arm.mass

    def printVars(self):
        attrs = vars(self)
        print(', \n'.join("%s: \t%s" % item for item in attrs.items()))
        print()


class Pointmass:
    def __init__(self, mass):
        self.mass = mass

        self.location = None


class Segment:
    def __init__(self, mass):
        self.mass = mass

        self.start = None
        self.end = None

In which

self.totalmass = self.joint1.mass + self.joint2.mass + self.joint3.mass + self.slide.mass + self.arm.mass

is a very long line, and is really inconvenient when the Robot gains more arms and joints... Is there a better way to obtain the total mass?

Answer 1

You shouldn't be storing the joints in separate attributes. Rather, store a simple joints list; then you can simply use sum with a generator expression.

self.totalmass = sum(j.mass for j in self.joints)