Redundancy Check issues #97

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1. OrangeTux commented on Jul 23, 2020

   

   OrangeTux

   on Jul 23, 2020

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   What do you mean? Instead of

       if not struct.unpack('<H', get_crc(msg[:-2])) ==\
               struct.unpack('<H', msg[-2:]):
           raise CRCError('CRC validation failed.')

   you suggest:

       if  struct.unpack('<H', get_crc(msg[:-2])) !=\
               struct.unpack('<H', msg[-2:]):
           raise CRCError('CRC validation failed.')
2. dmhouston95 commented on Jul 23, 2020

   

   dmhouston95

   on Jul 23, 2020

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   Yes. The expression evaluates false because not of an integer is always false unless the integer is zero. And then if you are trying to compare a boolean false (evaluated from the not expression) with an integer that will also always be false.
3. dmhouston95 commented on Jul 23, 2020

   

   dmhouston95

   on Jul 23, 2020

   Last edited by dmhouston95

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   This would also be vaild

   if not (struct.unpack('<H', get_crc(msg[:-2])) ==struct.unpack('<H', msg[-2:])):
           raise CRCError('CRC validation failed.')
   
4. rgov commented on Jul 24, 2020

   

   rgov

   on Jul 24, 2020

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   See operator precedence: https://docs.python.org/3/reference/expressions.html#operator-precedence

   not is less binding than == so I believe that not a == b is (in most cases?) the same as a != b. Since == and is have the same precedence, this is easier to see this way:

   >>> not 1
   False
   >>> not 1 is True
   True
   

   If not bound more tightly, then it would be the same as (not 1) is True which doesn't match the behavior. But instead we get not (1 is True).

   However != reads better to me.

   👍React with 👍1Reacted by David Houston