Hello World
註解
宣告
Python 有自動型別判斷 無須指定型別
i = 1
d = 1.0
s = "string"
b = True // False
arr = [1, 2, 3]
運算子
x = 2
y = 3
z = x + y
z = x - y
z = x * y
z = x / y
z = x // y # 只取整數解
z = x % y # 取餘數
z = x ** y # x的y次方
IF ELSE
grade = 90
if grade >= 90:
print('Excellent!')
elif grade >= 60:
print('Good enough!')
else:
print('Loser!')
For loop
arr = ["A", "B", "C", "D"]
# 印出value
for v in arr:
print(v)
# range
for i in range(0, len(arr)):
print(i)
# 印出 index, value
for i,v in enumerate(arr):
print(i, "->", v)
While loop
i = 0
while i < 10:
print(i)
if i == 3:
continue
if i >= 6:
break
else:
# while 第一次條件為 False 才會執行
print("i >= 10")
Function
def f():
print("hello python function")
def f(name):
print("hello ", name)
def f(name):
return "hello " + name
count = 0
def f():
global count // 宣告使用全域變數 count
count += 1
Class
class Cat:
name = "name"
def sound():
print("喵")
cat = Cat()
cat.name = "秀秀"
print(cat.name)
cat.sound()
建構子
class Cat:
def __init__(self, name):
# 建構子 建立物件時會呼叫
self.name = name
def sound(self):
print("喵")
cat = Cat("秀秀")
print(cat.name)
cat.sound()
如果有變數不想被外部使用可以使用兩個底線作為宣告
class Cat:
def __init__(self, name):
self.__name = name # 如果有變數不想被外部使用可以使用兩個底線作為宣告
cat = Cat("秀秀")
print(cat.name) # AttributeError: 'Cat' object has no attribute '__name'
繼承 Extends
class Animal():
def sound(self):
print("不知名的叫聲")
class Cat(Animal):
def __init__(self, name):
self.name = name
def sound(self):
print("喵")
cat = Cat("秀秀")
print(cat.name)
cat.sound()
python 也可以多重繼承
class Animal():
def sound(self):
print("不知名的叫聲")
class Cute():
def playingCute(self):
print("裝可愛")
class Cat(Animal, Cute):
def __init__(self, name):
self.name = name
def sound(self):
print("喵")
cat = Cat("秀秀")
print(cat.name)
cat.sound()
cat.playingCute()
抽象類別 Abstract class
Animal 未實作 voice 因此 Cat 在繼承後 必須實作
class Animal():
def sound(self):
print(self.voice) # voice 未實作
class Cat(Animal):
def __init__(self, name):
self.name = name
self.voice = "喵" # 實作 voice
cat = Cat("秀秀")
print(cat.name)
cat.sound()
上例說明 簡單的 abstract 但聰明的你應該也覺得怪怪的吧
那是因為 python 沒有 abstract class 或是 interface
是依照設計者的自我約束但 但是大家都知道的 呵呵
因此有 abc 庫來強制約束設計者
import abc
class Animal(abc.ABC):
@abc.abstractmethod
def sound(self):
return NotImplemented
class Cat(Animal):
def __init__(self, name):
self.name = name
def sound(self):
print("喵")
cat = Cat("秀秀")
print(cat.name)
cat.sound()
