[Python Learning Diary] Exception handling for Python

I. Exceptions

Python throws an exception when it encounters an error. If the exception object is not captured or processed, the program will backtrack (Traceback) to terminate the operation:

1 print 1/ 023Traceback (most recent call last):4   " D:\coding_file\python_file\TestPython\src\Test\test1.py "  in <module>5     print 1/ 06or modulo by Zero

Two. Throwing an exception

Python uses a class or instance argument to invoke the raise statement to throw an exception.

1 RaiseException ("It ' s an exception raised by me.")2 3 Traceback (most recent):4File"D:\coding_file\python_file\TestPython\src\Test\test1.py", Line 1,inch<module>5     RaiseException ("It ' s an exception raised by me.")6Exception:it's An exception raised by me.

Three: Catching multiple exceptions
Python uses try/except to catch exceptions. You can use a tuple to list multiple types of exceptions to achieve a block that captures multiple types of exceptions.

1 Try:2x = input ('Please enter the first number :')3y = input ('Please enter the second number:')4     PrintX/y5 except(Zerodivisionerror, TypeError) as E:6     Printe7  8 Input:9Please enter the first number:1Ten Please enter the second number:0 One  A Operation Result: -Integer divisionorModulo by zero

< Span style= "color: #0000ff;" >< Span style= "color: #008080;" >< Span style= "color: #0000ff;" > > Note: except (Zerodivisionerror, TypeError) as E: 
                 /span>        E is used for storing exception information, which can be used for subsequent printing exception information; Before Python 3.0 can writeexcept (Zerodivisionerror, TypeError), E:

Four. Require the user to re-enter
You can use a looping statement to make the program constantly require re-entry when an error occurs:  

1  whileTrue:2     Try:3x = input ('Please enter the first number :')4y = input ('Please enter the second number:')5result = x/y6         Print 'x/y equals', result7     except(Zerodivisionerror, TypeError) as E:8         Print 'Invalid Input:', E9         Print 'Please enter again.'Ten     Else: One          Break A  - Input: -Please enter the first number:1 the Please enter the second number:0 -  - Operation Result: -Invalid Input:integer Divisionormodulo by Zero + Please enter again. -Please enter the first number:

Program exits normally (via Else:break statement) when no exception occurs

Five. Cleanup after an exception occurs
The finally statement is used to clean up after possible exceptions

1 Try:2x = input ('x =?:')3y = input ('y =?:')4     PrintX/y5 except(Zerodivisionerror, TypeError, Nameerror) as E:6     Printe7 Else:8     Print 'No problem!'9 finally:Ten     Print ' done!'

In the above code, the finally clause is bound to be executed regardless of whether the try statement has an exception

[Python Learning Diary] Exception handling for Python