# Class slide ver. bearrrrrrro 2020/5/23 sylveon 2021/5/7 修改 --- ## 語法 ```python class ClassName: pass ``` ---- 加上一些東西 ```python class Computer: pass cp_1 = Computer() cp_1.cpu = 'i5-8750' cp_1.size = 14 cp_1.price = 20000 cp_2 = Computer() cp_2.cpu = 'i7-1450' cp_2.size = 10 cp_2.price = 2000 ``` ---- 試試看 ```python print(cp_1) print(cp_1.cpu) print(cp_2.price) ``` --- ## 作用  ---- * 好懂 * 易讀 * 減少重複性高的程式碼 * 看起來比較專業 XD ---- ## 概念 * 可以發揮你的想像力做出幾乎任何東西 * 自定義物件（資料型態？） * 當你想把某些狀態（資料）和功能（函式）綁在一起時，class是一個好選擇 ---- ## 一些不知道不影響你打code但是知道比較好的東西 * class 又稱為「類別」 * class 底下的資料又稱為「屬性」 * class 底下的函式又稱為「方法 (method)」 ---- ### 更多簡單的範例 電腦 ```python class Computer: def __init__(self, cpu, size, price): self.cpu = cpu self.size = size self.price = price ``` * 其中`__init__`是比較特殊的函式，會在「建構物件」時自動呼叫（後面有範例） * 這裡的 `xxx.yyy`指"xxx的yyy"，有點類似之前在import一些工具中的用法 ---- 人 ```python class Person: def __init__(self, name, height, weight): self.name = name self.height = height # cm self.weight = weight # kg def get_bmi(self): return self.weight / (self.height / 100) ** 2 ``` ---- baba ```python class Baba: def __init__(self, x, y): self.x = x self.y = y def up(self): self.x -= 1 def down(self): self.x += 1 def left(self): self.y -= 1 def right(self): self.y += 1 ``` ---- **Remark:** class中的函式第一個參數要放self，不然可能會噴錯或是發生奇怪的事情（？ ---- **Remark:** `__init__`中參數的名稱可以任意，像是我也可以這樣寫 ```python class Animal: def __init__(self, x): self.name = x ``` 但名稱不一致可能造成混淆而且沒有必要，除了可以少打幾個字以外沒有任何好處  --- ## 用class ---- ### Instance Instance 又稱為「實體」，依照class真的某個東西做出來 | Class | Instance | | -------- | -------- | | 設計圖 | 真正的東西 | ---- 有了class以後，我們可以造出多個狀態和功能類似的東西  ---- ```python cp_1 = Computer('i5-8750', 14, 20000) cp_2 = Computer('i7-1450', 10, 2000) print(cp_1) print(cp_1.cpu) print(cp_2.price) ``` ---- ```python bearrrrrrro = Person('bearrrrrrro', 170, 71) print(bearrrrrrro.name) print(bearrrrrrro.get_bmi()) ``` --- ## 連連看  ---- [解答](https://i.imgur.com/PPL9Hgg.png) --- ## 練習1 小明不小心把墨水打翻在他的code上，請幫小明通靈被墨水蓋掉的資訊 ```python class Student: def __init__(self, name, math, english, chinese): 墨墨墨墨墨 墨墨墨墨墨 墨墨墨墨墨 墨墨墨墨墨 def average(墨墨墨墨墨墨 墨墨墨墨墨 # 回傳三科的平均值 def is_pass(墨墨墨墨墨墨 墨墨墨墨墨 # 每一科都不低於60分就回傳true boss = Student('Sophia', 80, 100, 100) print(boss.average()) print(boss.is_pass()) ``` ---- ```python class Student: def __init__(self, name, math, english, chinese): self.name = name self.math = math self.english = english self.chinese = chinese def average(self): return sum((self.math, self.english, self.chinese)) / 3 # 回傳三科的平均值 def is_pass(self): return min((self.math, self.english, self.chinese)) >= 60 # 每一科都不低於60分就回傳true boss = Student('Sophia', 1000, 100, 100) print(boss.average()) print(boss.is_pass()) ``` --- ## 特殊方法(補充) + 練習2 ```python from math import gcd class Rational: def __init__(self, p, q): t = gcd(p, q) p, q = p // t, q // t self.p = p self.q = q def __str__(self): return '{}/{}'.format(self.p, self.q) def __add__(self, a): # print('{} + {}'.format(self, a)) nu = self.p * a.q + a.p * self.q di = self.q * a.q com = gcd(nu, di) return Rational(nu // com, di // com) # Your part here!! def __sub__(self, a): # x - y # print('{} - {}'.format(self, a)) pass def __mul__(self, a): # x * y # print('{} * {}'.format(self, a)) pass def __truediv__(self, a): # x / y # print('{} / {}'.format(self, a)) pass def __eq__(self, a): # x == y # print('{} == {}'.format(self, a)) pass if __name__ == '__main__': r = Rational(1, 4) s = Rational(3, 8) t = Rational(2, 8) print(r + s) print(r - s) print(r * s) print(r / s) print(r == s) print(r == t) ``` ---- 解答 ```python from math import gcd class Rational: def __init__(self, p, q): t = gcd(p, q) p, q = p // t, q // t self.p = p self.q = q def __str__(self): return '{}/{}'.format(self.p, self.q) def __add__(self, a): # print('{} + {}'.format(self, a)) nu = self.p * a.q + a.p * self.q di = self.q * a.q com = gcd(nu, di) return Rational(nu // com, di // com) # Your part here!! def __sub__(self, a): # x - y # print('{} - {}'.format(self, a)) nu = self.p * a.q - a.p * self.q di = self.q * a.q return Rational(nu, di) def __mul__(self, a): # x * y # print('{} * {}'.format(self, a)) nu = self.p * a.p di = self.q * a.q return Rational(nu, di) def __truediv__(self, a): # x / y # print('{} * {}'.format(self, a)) nu = self.p * a.q di = self.q * a.p return Rational(nu, di) def __eq__(self, a): # x == y # print('{} == {}'.format(self, a)) return self.p == a.p and self.q == a.q if __name__ == '__main__': r = Rational(1, 4) s = Rational(3, 8) t = Rational(2, 8) print(r + s) # Ratinal.__add__(r, s) print(r - s) print(r * s) print(r / s) print(r == s) print(r == t) ``` --- ## 繼承(補充)  ---- ```python class Dog: def __init__(self, name, color): self.name = name self.color = color def sound(self): print("Woof") class Cat: def __init__(self, name, weight): self.name = name self.weight = weight class Vampire: def __init__(self, name, age): self.name = name self.age = age def sound(self): print("Wryyyyyyyy!!") def time_stop(self): print("Za warudo!") ``` ---- Same! ```python class Animal: def __init__(self, name): self.name = name def hello(self): print(self.name) class Dog(Animal): def __init__(self, name, color): super().__init__(name) self.color = color def sound(self): print("Woof") class Cat(Animal): def __init__(self, name, weight): super().__init__(name) self.weight = weight class Vampire(Animal): def __init__(self, name, age): super().__init__(name) self.age = age def sound(self): print("Wryyyyyyyy!!") def time_stop(self): print("Za warudo!") ```