现在，如果程序员想要改变大小，他们可以，否则他们不必。我们可能还希望允许程序员修改blob的速度，如果他们想：

import random


class Blob:

    def __init__(self, color, x_boundary, y_boundary, size_range=(4,8), movement_range=(-1,2)):
        self.size = random.randrange(size_range[0],size_range[1])
        self.color = color
        self.x_boundary = x_boundary
        self.y_boundary = y_boundary
        self.x = random.randrange(0, self.x_boundary)
        self.y = random.randrange(0, self.y_boundary)
        self.movement_range = movement_range

    def move(self):
        self.move_x = random.randrange(self.movement_range[0],self.movement_range[1])
        self.move_y = random.randrange(self.movement_range[0],self.movement_range[1])
        self.x += self.move_x
        self.y += self.move_y

        if self.x  self.x_boundary: self.x = self.x_boundary
        
        if self.y  self.y_boundary: self.y = self.y_boundary

我们强制blob保持入界的线。可能有一些例子我们希望blob能够在视野中自由漫游吗？当然！这个边界代码有用吗？程序员是否可能想要经常使用它？当然！但是，要么根本没有代码，要么给它自己的方法更有意义，如下所示：

import random

class Blob:

    def __init__(self, color, x_boundary, y_boundary, size_range=(4,8), movement_range=(-1,2)):
        self.size = random.randrange(size_range[0],size_range[1])
        self.color = color
        self.x_boundary = x_boundary
        self.y_boundary = y_boundary
        self.x = random.randrange(0, self.x_boundary)
        self.y = random.randrange(0, self.y_boundary)
        self.movement_range = movement_range

    def move(self):
        self.move_x = random.randrange(self.movement_range[0],self.movement_range[1])
        self.move_y = random.randrange(self.movement_range[0],self.movement_range[1])
        self.x += self.move_x
        self.y += self.move_y

    def check_bounds(self):
        if self.x  self.x_boundary: self.x = self.x_boundary
        
        if self.y  self.y_boundary: self.y = self.y_boundary