1、建構函式__init__()

#coding=utf-8
class Student():
    name = ""
    age  = 0
    
    def __init__(self): #建構函式
        pass

    def do_homework(self):
        print(self.name +"do homework")


student1 = Student()
student2 = Student()
student3 = Student()

例項化的時候，python 會自動的呼叫建構函式，不需要去顯示呼叫，如果非要調，也可以

#coding=utf-8
class Student():
    name = ""
    age  = 0
    
    def __init__(self): #建構函式
        pass

    def do_homework(self):
        print(self.name +"do homework")


student1 = Student()
a = student1.__init__()
print(type(a))
# Project/python_ToolCodes/test6.py"
# <type 'NoneType'>

這個說明 顯示呼叫建構函式沒有什麼特別的，跟普通函式沒區別，且無返回值。如果非要返回

#coding=utf-8
class Student():
    name = ""
    age  = 0
    
    def __init__(self): #建構函式
        return "111"

    def do_homework(self):
        print(self.name +"do homework")


student1 = Student()
a = student1.__init__()
print(type(a))
# Project/python_ToolCodes/test6.py"
# Traceback (most recent call last):
 

#   File "/Users/anson/Documents/Project/python_ToolCodes/test6.py", line 13, in <module>
#     student1 = Student()
# TypeError: __init__() should return None

這就跟Java 一樣了，建構函式無返回值，如果非要強制返回，那就報錯了，因為python 和Java一樣 不允許在建構函式中返回

這樣也算是啥也不返回，和不寫return 是一樣的

#coding=utf-8
class Student():
    name = ""
    age  = 0
    
    def __init__(self): #建構函式
        return 

    def do_homework(self):
        print(self.name +"do homework")


student1 = Student()
a = student1.__init__()
print(type(a))
# Project/python_ToolCodes/test6.py"
# <type 'NoneType'>

2、帶參建構函式__init__(self,name,age)：用來初始化物件的屬性

#coding=utf-8
class Student():
    name = ""
    age  = 0
    
    def __init__(self,name,age): #建構函式
        self.name = name
        self.age  = age

    def do_homework(self):
        print(self.name +"do homework")


student1 = Student("ansonw",26)
print("name:"+student1.name)
print("age:"+str(student1.age))
# Project/python_ToolCodes/test6.py"
# name:ansonw
# age:26

3、類變數和例項變數（關於類變數的使用方法，似乎與Java 不同）

Student.name 和 student1.name

#coding=utf-8
class Student():
    name = "kiki"
    age  = 0
    
    def __init__(self,name,age): #建構函式
        self.name = name
        self.age  = age

    def do_homework(self):
        print(self.name +"do homework")


student1 = Student("ansonw",26)
print("例項變數=>name:"+student1.name)
print("類變數=>name:"+Student.name)
# 例項變數=>name:ansonw
# 類變數=>name:kiki

但是，類是不需要名字和年齡的，所以這裡類有名字為"kiki" 是不合理的

4、__dict__python內建變數列印，物件的內容和類的內容

student1.__dict__

物件：
#coding=utf-8
class Student():
    name = ""
    age  = 0
    
    def __init__(self,name,age): #建構函式
        self.name = name
        self.age  = age

    def do_homework(self):
        print(self.name +"do homework")


student1 = Student("ansonw",26)
print(student1.__dict__)
# [Running] python -u "/Users/anson/Documents/Project/python_ToolCodes/test6.py"
# {'age': 26, 'name': 'ansonw'}

類：
#coding=utf-8
class Student():
    name = ""
    age  = 0
    
    def __init__(self,name,age): #建構函式
        self.name = name
        self.age  = age

    def do_homework(self):
        print(self.name +"do homework")


student1 = Student("ansonw",26)
print(Student.__dict__)
#[Running] python -u "/Users/anson/Documents/Project/python_ToolCodes/test6.py"
#{'__module__': '__main__', 'do_homework': <function do_homework at 0x10ab0d758>, 'name': '', 'age': 0, '__doc__': None, '__init__': <function __init__ at 0x10ab0d140>}

5、python 中的self 與this

• Java 中的用this 來指代當前物件，python中可以用this，但是建議使用self
• 類方法定義時，必須要帶上self

• def __init__(self,name,age): #建構函式
          self.name = name
          self.age  = age
  
      def do_homework(self):
          print(self.name +"do homework")

• 類方法倍呼叫時，不需要帶self，因為python自動給我們加上了這個入參

• student1.do_homework()