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 eva l(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 eva l(expr)
TypeError: eva l() 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 eva l(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...