1.反射：

1.1定義：通過字符串映射或修改程序運行時的狀態、屬性、方法

1.2有以下四個方法：

（1）hasattr(object,str) 判斷object對象中是否有對應的方法或屬性，返回值：True·、False

class People(object):
    ‘‘‘this is the description of People‘‘‘
    def __init__(self,name,sex,age):
        self.name = name
        self.sex = sex
        self.age = age
    def eat(self):
        
 
print("%s is eating...."%self.name)
    def piao(self):
        print("%s is piaoing..."%self.name)
    def __call__(self, *args, **kwargs):
        print("My name is Mr Wu")
    def __str__(self):
        return "hello world"

man = People("dog","male",19)
if hasattr(man,"name") and hasattr(man,"eat
 
"):
    print("hello world!")
#output:hello world!

（2）func = getattr(object,str)根據str去獲取object對象中的對應的方法的內存地址或屬性的值(調用：func(argument))

class People(object):
    ‘‘‘this is the description of People‘‘‘
    def __init__(self,name,sex,age):
        self.name = name
        self.sex = sex
        self.age 
 
= age
    def eat(self):
        print("%s is eating...."%self.name)
    def piao(self):
        print("%s is piaoing..."%self.name)
    def __call__(self, *args, **kwargs):
        print("My name is Mr Wu")
    def __str__(self):
        return "hello world"

man = People("dog","male",19)
func = getattr(man,"eat")
func() #dog is eating....
name = getattr(man,"name")
print(name) #dog

（3）delattr(object,str) 刪除object對象中的str對應的方法或屬性

class People(object):
    ‘‘‘this is the description of People‘‘‘
    def __init__(self,name,sex,age):
        self.name = name
        self.sex = sex
        self.age = age
    def eat(self):
        print("%s is eating...."%self.name)
    def piao(self):
        print("%s is piaoing..."%self.name)
    def __call__(self, *args, **kwargs):
        print("My name is Mr Wu")
    def __str__(self):
        return "hello world"

man = People("dog","male",19)
delattr(man,"name")
print(man.name) #AttributeError: ‘People‘ object has no attribute ‘name‘
delattr(man,"eat")
man.eat()#AttributeError: eat

（4）setattr(x,y,v)相當於x.y = v，設置新的屬性或方法（可修改原有的屬性和方法）

class People(object):
    ‘‘‘this is the description of People‘‘‘
    def __init__(self,name,sex,age):
        self.name = name
        self.sex = sex
        self.age = age
    def eat(self):
        print("%s is eating...."%self.name)
    def piao(self):
        print("%s is piaoing..."%self.name)

def sleep(self):
    print("%s is sleeping...."%(self.name))
name = "Mr Wu"

man = People("dog","male",19)
setattr(man,"sleep",sleep)
man.sleep(man) #dog is sleeping....
setattr(man,"name",name)
print(man.name) #Mr Wu

2.異常處理

2.1 概述：

Python的異常處理能力是很強大的，可向用戶準確反饋出錯信息。在Python中，異常也是對象，可對它進行操作。所有異常都是基類Exception的成員。所有異常都從基類Exception繼承，而且都在exceptions模塊中定義。Python自動將所有異常名稱放在內建命名空間中，所以程序不必導入exceptions模塊即可使用異常。一旦引發而且沒有捕捉SystemExit異常，程序執行就會終止。如果交互式會話遇到一個未被捕捉的SystemExit異常，會話就會終止。

2.2 python中所有的標準異常類

2.2 語法格式

try:

代碼塊

except 異常名稱 as e:

print(e) #輸出異常的內容

except 異常名稱 as e:

print(e) #輸出異常處理

...............

特別地：

except Exception as e:

#如果不知道異常具體是什麽類型，可以使用Exception

else:

#如果沒有出現前面的異常則執行這條語句

finally:
#不管有沒有出現前面的異常都會執行這條語句

註：如果已經捕獲到了try下的一條異常，那麽就不會再捕獲其他異常了

代碼實例：

names = ["Mr Wu","Ms Li"]
dict_names = {"name":"Mr Wu","age":19}
try:
    print(names[3])
    dict_names["Mr Wang"]
except IndexError as e:
    print("出錯了:",e)
except KeyError as e:
    print("出錯了:",e)
except Exception as e:
    print("未知錯誤:",e)
#output：出錯了: list index out of range

names = ["Mr Wu","Ms Li"]
dict_names = {"name":"Mr Wu","age":19}
try:
    print(names[3])
    dict_names["Mr Wang"]
#except IndexError as e:
#    print("出錯了:",e)
#except KeyError as e:
#    print("出錯了:",e)
except Exception as e:
    print("未知錯誤:",e)
#output：未知錯誤: list index out of range

2.3 自定義異常

我們可以自己定義異常類，並且觸發執行這個異常。

註：自定義的異常必須繼承異常類基類Exception，並通過raise語句實例化這個類

class AlexException(Exception):
    def __init__(self,msg):
        self.message = msg
try:
    raise AlexException("\033[1;41m數據庫連接失敗\033[0m")
except AlexException as e:
    print(e)
#output：數據庫連接失敗

python第七周學習內容