#!/usr/bin/env python
# -*- coding: utf-8 -*-
# @Time : 2018/10/17 14:24
# @Author : Ropon
# @File : 20_01.py
# 异常是什么，比如：
# IndexError [][1]
# KeyError {}['key']
# EOFError pickle.load()
# FileNotFoundError open('aaaa')
# ModuleNotFoundError import aaaaaaadfdsdf
# ValueError int('dsfsdfsdf')
# 语法错误，编写代码时就应该规避掉
# SyntaxError
# NameError name
# 什么时候容易出现异常，当您输入的内容不确定，比如：
# 有用户参与输入
# 有外界数据介入，比如从文件中读，从网络中获取
# 多行报错的原因是:一般在嵌套调用过程中,内部代码出现异常,外部所有调用的地方都成为报错追溯信息的一部分
# def func1():
# name
#
# def func2():
# func1()
#
# def func3():
# func2()
#
# def main():
# func3()
#
# main()
# 遇到多行报错，如何分析
# 从下往上分析，逐个检查出错行，分析您自己写的代码
# 如果找不到问题，就将最后一行的错误类型及详细提示复制到百度搜索
# lst = ['login', 'register']
# for num, i in enumerate(lst , 1):
# print(num, i)
#
# try:
# num = int(input("num >>"))
# print(lst[num - 1])
# except ValueError:
# print("请输入一个数字")
# lst = ['login', 'register']
# for num, i in enumerate(lst , 1):
# print(num, i)
# try:
# num = int(input("num >>"))
# print(lst[num - 1])
# except ValueError:
# # 从上往下错误代码，匹配到一个报错类型分支就执行这个分支中的代码，然后退出分支
# print("请输入一个数字")
# except IndexError:
# # 如果找不到匹配的分支，就一直往下查找，最后依然没有找到匹配就报错
# print("只能输入1或2")
#合并多分支
# lst = ['login', 'register']
# for num, i in enumerate(lst , 1):
# print(num, i)
# try:
# num = int(input("num >>"))
# print(lst[num - 1])
# except (ValueError, IndexError):
# print("输入不合法")
#万能异常
# def buy():
# print("buy")
# name
#
# def back():
# print("back")
# [][1]
#
# def show():
# print("show")
# 1/0
#
# def main():
# lst = [('购物', buy), ('退货', back), ('查看订单', show)]
# while 1:
# for num, i in enumerate(lst, 1):
# print(num, i[0])
# num = int(input("num >>>"))
# try:
# print(lst[num - 1])
# func = lst[num - 1][1]
# func()
# except (ValueError, IndexError):
# print('您输入的内容不合法')
# except Exception:
# print("用户选择%s操作之后发生未知错误" % lst[num - 1][0])
#
# if __name__ == '__main__':
# main()
# as语法 能够将具体错误信息打印出来
# def buy():
# print("buy")
# name
#
# def back():
# print("back")
# [][1]
#
# def show():
# print("show")
# 1/0
#
# def main():
# lst = [('购物', buy), ('退货', back), ('查看订单', show)]
# while 1:
# for num, i in enumerate(lst, 1):
# print(num, i[0])
# num = int(input("num >>>"))
# print(lst[num - 1])
# try:
# func = lst[num - 1][1]
# func()
# except Exception as e:
# print(e)
# print("用户选择%s操作之后发生未知错误" % lst[num - 1][0])
#
# if __name__ == '__main__':
# main()
# 万能异常相当于except Exception
# try:
# name
# [][1]
# int('aaa')
# # except:
# except Exception:
# print("123")
# 多分支 万能异常，万能异常应该永远放到异常处理最下面
# def buy():
# print("buy")
# name
#
# def back():
# print("back")
# [][1]
#
# def show():
# print("show")
# 1/0
#
# def main():
# lst = [('购物', buy), ('退货', back), ('查看订单', show)]
# while 1:
# for num, i in enumerate(lst, 1):
# print(num, i[0])
# num = int(input("num >>>"))
# try:
# print(lst[num - 1])
# func = lst[num - 1][1]
# func()
# except (ValueError, IndexError):
# print('您输入的内容不合法')
# except Exception:
# print("用户选择%s操作之后发生未知错误" % lst[num - 1][0])
#
# if __name__ == '__main__':
# main()
# 总结
# try:
# pass
# except (ValueError,IndexError):
# print("针对性处理异常")
# except Exception as e:
# print("通用办法处理异常")
# else分支
# try:
# print("test")
# # name
# # [][1]
# # 1/0
# except NameError:
# print("NameError")
# except IndexError:
# print("IndexError")
# except Exception as e:
# print(e)
# else:
# print("else")
# finally分支
# try:
# print("test")
# # name
# # [][1]
# # 1/0
# except NameError:
# print("NameError")
# except IndexError:
# print("IndexError")
# except Exception as e:
# print(e)
# else:
# print("else")
# finally: # 无论如何都会被执行
# print("finally")
# def func():
# f = open('test.txt', 'r')
# try:
# while 1:
# for line in f:
# if line.startswith('a'):
# return line
# except:
# print("异常处理")
# finally: # 即使return也会先执行fianlly中的代码
# f.close()
#
# print(func())
# try:
# f = open('test.txt', 'r')
# f.read()
# name
# finally: #即使程序报错，在程序结束之前也会执行此分支代码
# f.close()
# print("已关闭打开的文件")
# finally 通常用来回收一些系统的资源，比如数据连接，打开的文件，网络连接等
# 异常处理常用：
# try ... except
# try ... except ... else
# try ... finally
# try ... except ... finally
# try ... except ... else ... finally
# 主动抛出异常，主要是给其他开发者看的
# raise ValueError("你写的不正确")
# python assert断言是声明其布尔值必须为真的判定，如果发生异常就说明表达示为假。
# 可以理解assert断言语句为raise-if-not，用来测试表示式，其返回值为假，就会触发异常。
# assert 2==1 False
# assert 1==1 True
# print("test")
# if 1 == int(input()):
# print("test")
# else:
# raise AssertionError
# 自定义异常
# 最外层的异常处理应该在所有开发完成后才考虑，一般最后将错误写到文件中。
# def main():
# name
# try:
# main()
# except Exception as e:
# with open('error.log', 'a', encoding='utf-8') as f:
# f.write(str(e))
