11.异常处理 断言

异常处理方法：
try:
except:
...
except:
else:
finally:

try:
    a = input("请输入数字")
    b = int(a)
except Exception as e:  # Exception万能异常情况
    print("错误了",e)
else:
    print("try内没有异常出现  才会执行这里")
finally:
    print("完毕")

---

使用raise主动触发异常：

try:
    a = input("请输入数字")
    b = int(a)
    raise ValueError("错误了")
except Exception as e:  # Exception万能异常情况
    print("错误了",e)

---

自定义异常

class NewError(BaseException):
    def __init__(self, msg):
        self.msg = msg

raise NewError("哈哈")

---

断言

使用assert关键字

assert a == b
# 断定a跟b相等