Python学习笔记：2.2.3 习题课06

Posted 2023-01-06 WinvenChang

本文是学习齐老师的《python全栈工程师》课程的笔记，欢迎学习交流。同时感谢齐老师的精彩传授！

习题01：

• 创建类SchoolKid，初始化小孩的姓名、年龄，并且有访问和修改属性的方法。然后创建类ExaggeatingKid，继承SchoolKid，子类中覆盖父类中访问年龄的方法，并将实际年龄增加2.

class SchoolKid:
	def __init__(self, name, age):
		self.name = name
		self.age = age
		
	def change_name(self, new_name):
		self.name = new_name
		return self.name
	def chang_age(self, new_age):
		self.age = age
		return self.age
	def get(self, attr='name')
		if attr == 'name':
			return self.name
		elif attr == 'age':
			return self.age
		else:
			print('There was not ' , attr)
			return None

class ExaggeratingKid(SchoolKid):
	def get(self, attr='name'):
		if attr == 'name':
			return self.name
		elif attr == 'age':
			return self.age + 2
		else:
			print('There was not ' , attr)
			return None

习题2：

• 内置函数range的参数必须是整数。请编写一个生成器函数，以浮点数为参数（开始值，结束值，步长）生成某范围的序列。

import itertools
def frange(start, end=None, step=1.0):
	if end is None:
		end = float(start)
		start = 0.0
	assert step # 当step不为True时，抛出错误
	for i in itertools.count():
		nxt = start + i * step
		if (step > 0.0 and nxt >= end) or (step < 0.0 and nxt <= end):
			break
		yield nxt
f = frange(1.2, 9)
print(list(f)) # [1.2, 2.2, 3.2, 4.2, 5.2, 6.2, 7.2, 8.2]

习题3：

• 编写一个关于矩形的对象类型，能够通过长、宽配置属性值
• 进 一步完善例题3的代码，让其使用起来更稳健。

class Rectangle:
    def __init__(self):
      self.width = 0
      self.length = 0

    def __getattr__(self, name):
        if name == 'size':
          return self.width, self.length
        else:
            raise AttributeError

    def __setattr__(self, name, value):
       # 此处增加了 try/except代码
        try:
          if name == 'size':        
              self.width, self.length = value                
          else:
            self.__dict__[name] = value        
        except TypeError:
          print('There are two numbers!')
          
rect = Rectangle()
rect.width = 3
rect.length = 4
print(rect.size)
print('---'*15)

rect.size = 30
print(rect.width)
print(rect.length)

运行结果：

习题4：

• 分数的表示形式如3/2这样，但是这种形式在python中是按照除法进行处理。Python的内置对象类型中又没有分数类型（不仅Python没有，是相当多高级语言都没有），所以，有必要自定义一个相关的类型。
• 附加题：在上述基础上，实现分数加法运算

class Fraction:
	def __init__(self, number, denom=1):
		self.number = number
		self.denom = denom
	def __str__(self):
		return str(self.number) + '/' + str(self.denom)
	
	__repr__ = __str__
f = Fraction(2, 3)
print(f) # 2/3

分数相加流程：

class Fraction:
	def __init__(self, number, denom = 1):
		self.number = number
		self.denom = denom
	
	def __str__(self):
		return str(self.number) + '/' + str(self.denom)
	
	__repr__ = __str__
	
	@staticmethod
	def gcd(a, b): # 最大公约数
		if not a > b:
			a, b = b, a
		while b != 0:
			remainder = a % b
			a, b = b, remainder
		return a
	@staticmethod
	def lcm(a, b): # 最小公倍数
		return (a * b) / Fraction.gcd(a, b)
	
	def __add__(self, other):
		lcm_num = Fraction.lcm(self.denom, other.denom)
		number_num = (lcm_num / self.denom * self.number ) + (lcm_num / other.denom * other.number)
		return Fraction(number_num, lcm_num)

m = Fraction(1, 3)
n = Fraction(1, 2)
s = m + n
print(s)

运行结果：