异常处理

try:
    #print('代码块，或者你要写的逻辑')
    # int('wewe')
    list1 = [1,2,4,5,6]
    # list1[666]
except ValueError as e:
    print('ValueError',e)
except IndexError as e :
    print('IndexError',e)
except Exception as e:#放在最后，包含所有的错误
    print('如果上个代码块执行出错，执行此代码块')
else:
    print('最开始代码块有错就不执行else，没错就执行else')

finally:
    print('代码不管出错不出错都会执行该代码！')




print('*'*12+'主动触发异常'+'*'*12)

try:
    #int('eeee')
    print('hhhh')
    raise Exception('主动跳出异常')#放在try代码块中
except Exception as e :
    print(e)



print('例子应用场景')
def  db():
    '''数据库函数'''
    return  False

def index():
    try:
        result = db()
        # int('eee')
        if result == False:#数据库执行出现问题
            raise  Exception('数据库执行出现问题')
    except Exception as e:
        str_error = str(e)
        print(str_error)
        r = open('error.txt','a',encoding = 'utf-8')
        r.write(str_error)
        r.write('\n')

index()



print('*'*12+'自定义异常方法'+'*'*12)

class OldBoy(Exception):
    def __init__(self,msg):
        self.message = msg


    def __str__(self):
        return self.message

try:
   raise OldBoy('我错了.....')
except Exception as e:#e---->oldboy
    print(e)