[Tutor] Overriding equality tests in Python

[Dave Angel]

On 03/23/2013 12:08 AM, Robert Sjoblom wrote:

You already got lots of good answers.  But I want to explicitly point 
out a bug in your code (2 places) that was only indirectly mentioned.

      <SNIP>


> class Outcome():
>    def __init__(self, name): #Ignoring odds for now
>      self.name = name
>
>    def __eq__(self, other):
>      '''returns True if Outcome.name matches other.name''':
>      if self.name == other.name: return True

Here your method returns either True or None. You never supply a return 
value of False, you just let the default None get returned.  For most 
purposes that will work, but it's a problem waiting to happen.

In this particular case, it's easiest to just return the expression:
       self.name == other.name

which already has a value of True or False.  But if the function were 
more complex, you'd want to make sure that all paths through it will 
return the value you desire, and not the default None.

     def my_method(self, other):
       '''returns True if Outcome.name matches other.name and False 
otherwise''':
       if self.name == other.name: return True
       return False




-- 
DaveA