异常处理

class MyException(Exception):
    """
    自定义异常,继承Exception
    """
    def __init__(self, msg):
        self.msg = msg

    def __str__(self):
        """
        当实例化对象后,print对象将打印该值
        """
        return self.msg

myexception = MyException
try:

    num1 = input("num1:")
    num2 = input("num2")
    num1 = int(num1)
    num2 = int(num2)
    result = num1 + num2
    print(result)
    raise myexception("yes. it's ok")
except ValueError as v:
    print("value error", v)
except myexception as e:
    print(e)
except KeyboardInterrupt:
    print("上面无法抓住终止")
except InterruptedError:
    print("test")
except SyntaxError:
    print("该异常无法捕获")
except IndentationError:
    print("该异常依然无法捕获")
except Exception:
    print("no")
else:
    print("一般测试用例,或者安装,可以使用,比如安装成功,没有错误")
finally:
    print("不管前面什么错,最终都会执行这里,除了语法,缩进以外")

断言

断言一般用于条件匹配，如果条件不满足，则不会进行下去，除非刻意去捕获处理

a = ["1", "2", "3"]
filter_a = filter(lambda i: int(i) < 2, a)
print(list(filter_a))
try:
    assert len(list(filter_a)) == len(a)
    
except AssertionError:
    print("条件不匹配,")