custom classes in sets

[Steven Bethard]

vegetax wrote:
> How can i make my custom class an element of a set?
> 
> class Cfile:
>   def __init__(s,path): s.path = path
> 
>   def __eq__(s,other):
>    print 'inside equals'
>    return not os.popen('cmp %s %s' % (s.path,other.path)).read()
> 
>   def __hashcode__(s): return s.path.__hashcode__()
> 
> the idea is that it accepts file paths and construct a set of unique 
> files (the command "cmp" compares files byte by byte.),the files can
> have different paths but the same content
> 
> but the method __eq__ is never called

Seems to be called fine for me:

py> class Cfile:
...     def __eq__(self, other):
...         print 'inside equals'
...         return False
...     def __hash__(self):
...         return 0
...
py> {Cfile():1, Cfile():2}
inside equals
{<__main__.Cfile instance at 0x01166490>: 1, <__main__.Cfile instance at 
0x01166760>: 2}

Note that __eq__ won't be called if the hashes are different:

py> class Cfile:
...     hash = 0
...     def __eq__(self, other):
...         print 'inside equals'
...         return False
...     def __hash__(self):
...         Cfile.hash += 1
...         return Cfile.hash
...
py> {Cfile():1, Cfile():2}
{<__main__.Cfile instance at 0x01166918>: 1, <__main__.Cfile instance at 
0x011668A0>: 2}

Steve