python 学习---错误 & 异常1

1. 错误&异常概述

获取BaseException

#!/usr/bin/env python3
# -*- encoding: utf-8 -*-
def classtree(cls, indent=0):
    print('.' * indent, cls.__name__)
    for subcls in cls.__subclasses__():
        classtree(subcls, indent + 3)

classtree(BaseException)

2. Try except 语法详解

代码示例：

#!/usr/bin/env python3
# -*- encoding: utf-8 -*-
while True:
    try:
        x = float(input("Please enter a number:"))
        break
    except ValueError:
        print("Oops! That was no valid number. Try again...")
        continue

#!/usr/bin/env python3
# -*- encoding: utf-8 -*-
def main():
    try:
        number1, number2 = eval(input("Enter two numbers, separated by a comma:"))
        result = number1 / number2

    except ZeroDivisionError:
        print("Division by zero!")
    except SyntaxError:
        print("A comma may be missing in the input")
    except:
        print("Something wrong in the input")
    else:
        print("No exceptions, the result is", result)
    finally:
        print("executing the final clause")

main()