python中异常的介绍
每个异常都是一 些类的实例,这些实例可以被引发,并且可以用很多种方法进行捕捉,使得程序可以捉住错误并且对其进行处理
>>> 1/0 Traceback (most recent call last): File "<pyshell#0>", line 1, in <module> 1/0 ZeroDivisionError: integer division or modulo by zero
异常处理
捕捉异常可以使用try/except语句。
>>> def inputnum(): x=input('Enter the first number: ') y=input('Enter the first number: ') try: print x/y except ZeroDivisionError: print "The second number can't be zero" >>> inputnum() Enter the first number: 10 Enter the first number: 0 The second number can't be zero
raise 触发异常
>>> class Muff: muffled=False def calc(self,expr): try: return eval(expr) except ZeroDivisionError: if self.muffled: print 'Division by zero is illegal' else: raise >>> c=Muff() >>> c.calc(10/2) Traceback (most recent call last): File "<pyshell#33>", line 1, in <module> c.calc(10/2) File "<pyshell#31>", line 5, in calc return eval(expr) TypeError: eval() arg 1 must be a string or code object >>> c.calc('10/2') 5 >>> c.calc('1/0') Traceback (most recent call last): File "<pyshell#35>", line 1, in <module> c.calc('1/0') File "<pyshell#31>", line 5, in calc return eval(expr) File "<string>", line 1, in <module> ZeroDivisionError: integer division or modulo by zero >>> c.muffled=True >>> c.calc('1/0') Division by zero is illegal
多种异常类型
try: x=input('Enter the first number:') y=input('Enter the seconed number:') print x/y except ZeroDivisionError: print "The second number can't be zero!" except TypeError: print "That wasn't a number,was it?"
同时 捕捉多个异常
try: x=input('Enter the first number:') y=input('Enter the seconed number:') print x/y except(ZeroDivisionError,TypeError,NameError): print 'Your numbers were bogus...'
捕捉对象
try: x=input('Enter the first number:') y=input('Enter the seconed number:') print x/y except(ZeroDivisionError,TypeError),e: print e Enter the first number:1 Enter the seconed number:0 integer division or modulo by zero
捕捉所有异常
try: x=input('Enter the first number:') y=input('Enter the seconed number:') print x/y except: print 'something wrong happened...' Enter the first number: something wrong happened...
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