2007/10/26, Robert Miller <[EMAIL PROTECTED]>: > I have some questions about Python comparison. Suppose I have a Python > class representing objects under some ordering, and I want to > implement <=, <, >=, >, ==, != comparisons on those objects. I > remember hearing somewhere that the __cmp__ method was deprecated, but > now that I am thinking about it I can't find anything confirming that. > Is there any reason to implement the functions __eq__, __neq__, > __gt__, __ge__, __lt__, __le__, instead of just one __cmp__? Including > forward compatibility, being more Python-ic or anything else?
I don't think __cmp__ is deprecated. From the docs (http://docs.python.org/ref/customization.html), it looks like __le__, __lt__, etc are called in preference to __cmp__ if they are defined. Otherwise, __cmp__() is called. I think one main reason for using these is to define more fine-grained relationships (partial ordering): """ There are no implied relationships among the comparison operators. The truth of x==y does not imply that x!=y is false. Accordingly, when defining __eq__(), one should also define __ne__() so that the operators will behave as expected. """ So, just use __cmp__ and if you want to overload != for example, just write your own __ne__ didier --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-devel@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sage-devel URLs: http://sage.scipy.org/sage/ and http://modular.math.washington.edu/sage/ -~----------~----~----~----~------~----~------~--~---
