Python20 error, debugging

Error, debugging

• Error handling:在程序运行的过程中，如果发生了错误，可以事先约定返回一个错误代码，这样，就可以知道是否有错，以及出错的原因
  • try ... except ... finally ... error handling mechanism

    • Code:
      `` `
      # exception handling
      # try ... except ... finally ...

      '' '
      When we think some of the code may be wrong, you can try to run this code,
      if executed wrong, then the following code will not continue, but the error-handling code to jump directly to that except statement block ,
      after executing except, if there is finally block, the finally block execute, so far, it is finished.
      '' '

      try: # statement is executed first come try print (10/0) in the block of statements
      Print (10/0)
      except the ZeroDivisionError: # try block error, execute block except statement, except statement if the block is not being given the try block is not performed
      print ( '! except statement is executed')
      finally: # no matter except whether the final will execute the finally block, you can not finally statement
      print ( '! finally statement is executed')
      Print ( 'test is completed!')
      `` `
    • operation result:
      
  • Record error: Python built-in logging module can easily record the error message

    • Code:
      `` `
      # built-in functions logging error messages are logged

      # Is also a mistake, but after the program finishes printing error message continues, and exit to normal:
      Import logging
      DEF do_ZeroError (vaule):
      return 10 / vaule

      def man():
      try:
      do_ZeroError(0)
      except Exception:
      logging.exception(Exception)
      man()
      print('End')
      ```
    • operation result:
      
  • Throw an error:raise

    • Code:
      `` `
      # raise throw an error

      # A custom error, error class inheritance need
      class TestError is (a ValueError):
      Pass
      DEF do_Return (I):
      IF I == 0:
      The raise TestError is ( 'wrong!')
      Return 10 / I

      print(do_Return(0))
      ```
• Debugging: means to check whether correct operation of the program
  • Assertion: assertmean, n = 0 expression should be True, otherwise, according to the logic of the program is running, the code behind will certainly be wrong!.
  • Example:
    
  • logging:
  • Example: