在python中異常的分析

每個異常都是一些類別的實例，這些實例可以被引發，並且可以用很多種方法進行捕捉，使得程式可以捉住錯誤並且對其進行處理

>>> 1/0

Traceback (most recent call last):
  File "<pyshell#0>", line 1, in <module>
    1/0
ZeroDivisionError: integer division or modulo by zero

異常處理

捕捉異常可以使用try/except語句。

>>> 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 觸發異常

>>> 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(&#39;10/2&#39;)
>>> c.calc(&#39;1/0&#39;)

Traceback (most recent call last):
  File "<pyshell#35>", line 1, in <module>
    c.calc(&#39;1/0&#39;)
  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(&#39;1/0&#39;)
Division by zero is illegal

多種異常類型

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?"

同時 捕捉多個例外

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...'

 捕捉物件

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

 捕捉所有異常

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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