Python基础教程之错误和异常的处理方法

# 异常的捕获
a=int(input(\'输入除数:\'))
b=int(input(\'输入被除数:\'))
try:
    res=a/b
except ZeroDivisionError:
    print(\'除数不可以为0\')
    # 相同处理方式的异常可以这么写
except (BaseException,TypeError):
    print(\'有错误\')
else:
    print(\'您的结果为\',res)
finally:
    print(\'感谢使用!\')

\'\'\'
3 录入一个学生的成绩，把该学生的成绩转换为A优秀、B良好、C合格、D不及格的形式，
最后将该学生的成绩打印出来。要求使用assert断言处理分数不合理(小于0或者大于100)的情况
请编写程序。
\'\'\'

n=int(input())
assert n in range(101),\"您输入的成绩不合理！\"
if n>=85:
	print(\"优秀！\")
elif n>=70:
	print(\"良好！\")
elif n>=60:
	print(\"合格！\")
else:
	print(\"不及格！\")

\'\'\'
自己定义一个异常类，继承Exception类, 捕获下面的过程：判断input()输入的字符串长度是否小于5， 
如果小于5，比如输入长度为3则输出:\"The input is of length 3, expecting at least 5“，
大于5则输出\"success”。 
\'\'\'
class StrLenError(Exception):
	def __init__(self,s):
		Exception.__init__(self,s)
		self.s =s
	def __str__(self):
			return f\"The input is of length {len(self.s)}, expecting at least 5\"
n=input()
if len(n)<=5:
	raise StrLenError(n)
else:
	print(\"success\")

>>> class NewError(Exception):
        def __init__(self, value):
            self.value = value
        def __str__(self):
            return repr(self.value)
   
>>> try:
        raise NewError(2*2)
    except NewError as e:
        print(\'New exception occurred, value:\', e.value)
   
My exception occurred, value: 4
>>> raise NewError(\'oops!\')
Traceback (most recent call last):
  File \"\", line 1, in ?
__main__.NewError: \'oops!\'

class Error(Exception):
    \"\"\"Base class for exceptions in this module.\"\"\"
    pass

class InputError(Error):
    \"\"\"Exception raised for errors in the input.

    Attributes:
        expression -- input expression in which the error occurred
        message -- explanation of the error
    \"\"\"

    def __init__(self, expression, message):
        self.expression = expression
        self.message = message

class TransitionError(Error):
    \"\"\"Raised when an operation attempts a state transition that\'s not
    allowed.

    Attributes:
        previous -- state at beginning of transition
        next -- attempted new state
        message -- explanation of why the specific transition is not allowed
    \"\"\"

    def __init__(self, previous, next, message):
        self.previous = previous
        self.next = next
        self.message = message