Python异常编码处理

1.主动触发异常

• raise

  raise TypeErrorraise TypeError('Error Message')    #添加错误提示

• assert

  a = 1assert a > 0assert a > 0,"a must lg 0"    #添加错误提示

2.处理特定异常

• try/except

  try:  int('hello')except ValueError:  print('invaild value')try:  int('hello')except ValueError as e:  print(e)

3.处理多个异常

• 用元组包含多种异常

  try:    file = open('test.txt', 'r')except (IOError, EOFError) as e:    print "error occurred:", e

• 多个except语句

  try:    file = open('test.txt', 'r')except (IOError, EOFError) as e:    print "error occurred:", e

• 捕获所有异常

  try:    3 / 0except:    print "error occurred"

• 使用Exception捕获异常

  try:    "123" / 2except Exception as e:    print e.message

4.else/finally语句

#异常没有触发时执行else后的代码try:    f=open('123.txt','w')    f.write({'name':'ming'})except Exception as e:    print('Error:'e)else:    f.write({'age':18})    f.close()    print('file has closed')#不管有没有触发异常,都会执行finally后的代码try:    f=open('123.txt','w')    print(f.write({'name':'ming'}))except Exception as e:    print('Error:'e)finally:    f.close()    print('file has closed')

5.自定义异常

当现存的异常类型没有自己想要的效果时,可以自己创建属于自己的异常类型

class RangeError(Exception):    #添加错误提示    def __str__(self):        return repr('the value out of range')def process(value):      if value < 0 or value > 10000:        raise RangeError    pass