Concise Python Tutorial Learn note 9

13. Abnormal

(1) Error

Some invalid statements in the program, such as syntax errors, are as follows:

1 " AA " 2 syntaxerror:invalid Syntax 3 Print " AA " 4 AA 5

(2) Try...except

1>>> s = raw_input ("Enter something --")2Enter something--and #这里期望输入, but the actual execution of Ctrl+d causes the following exception3 4 Traceback (most recent):5File"<pyshell#4>", Line 1,inch<module>6s = raw_input ("Enter something --")7 eoferror:eof When reading a line8>>>

You can use Try...except to handle exceptions

1 #-*-coding:utf-8-*-2 3 ImportSYS4 5 Try:6s = raw_input ("Enter something --")7 exceptEoferror:8     Print "\nwhy did yo do a EOF on me?"9Sys.exit ()#Exit The programTen except: One     Print "\nsome error/exception occurred." A     #Here , we aren't exiting the program -  - Print " Done"

Output:

(3) Exception thrown

You can use a raise statement to throw an exception .

Also specify the name of the error/exception and the exception object that accompanies the exception.

The error or exception that can be thrown should be Error a Exception direct or indirect export class of one or class.

1 #-*-coding:utf-8-*-2 3 4 classshortinputexception (Exception):5     """A user-defined Exception class."""6 7     def __init__(self, length, atleast):8Exception.__init__(self)9Self.length =lengthTenSelf.atleast =atleast One  A  - Try: -s = raw_input ("Enter something --") the     ifLen (s) < 3: -         Raise Shortinputexception (Len (s), 3) -         #Other work can continue as usual here - exceptEoferror: +     Print "\nwhy did you do a EOF on me?" - exceptshortinputexception, x: +     Print "shortinputexception:the input was of length%d,was expecting at least%d"%(X.length, X.atleast) A Else: at     Print "No exception was raised."

Output:

(4) try...finally

Do you want to do something without exception or not?

This can be finally done using blocks.

Concise Python Tutorial Learn note 9