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Benjamin Bandt-Horn

Elegant ways to support equivalence ("equality") in Python classes - Stack Overflow - 0 views

stackoverflow.com/...nce-equality-in-python-classes

equality operator python override

shared by Benjamin Bandt-Horn on 29 Dec 13 - Cached
  • mixin class
  • Another issue with the __dict__ comparison is what if you have an attribute that you don't want to consider in your definition of equality (say for example a unique object id, or metadata like a time created stamp).
  • isinstance sucks
  • ...4 more annotations...
  • if type(other) is type(self):
  • Check types more strictly, like this:
  • is tests for object identity. This means a is b will be True in the case when a and b both hold the reference to the same object
  • __cmp__ was removed from python 3 so avoid it
  • Benjamin Bandt-Horn on 29 Dec 13
     
    mixin class
Benjamin Bandt-Horn

jcalderone: How to override comparison operators in Python - 0 views

jcalderone.livejournal.com/32837.html

comparison operators python override

shared by Benjamin Bandt-Horn on 29 Dec 13 - No Cached
  • here are the basic rules for the customization of ==, !=, <, >, <=, and >=: For all six of the above operators, if __cmp__ is defined on the left-hand argument, it is called with the right-hand argument. A result of -1 indicates the LHS is less than the RHS. A result of 0 indicates they are equal. A result of 1 indicates the LHS is greater than the RHS
  • __eq__ is not used for !=
  • For <, __lt__ is used. For >, __gt__. For <= and >=, __le__ and __ge__ respectively
  • ...1 more annotation...
  • __eq__ does an isinstance test on its argument
  • Benjamin Bandt-Horn on 29 Dec 13
     
    here are the basic rules for the customization of ==, !=, , =: For all six of the above operators, if __cmp__ is defined on the left-hand argument, it is called with the right-hand argument. A result of -1 indicates the LHS is less than the RHS. A result of 0 indicates they are equal. A result of 1 indicates the LHS is greater than the RHS.
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