python bug when subclassing list?

Hamish McKenzie hamish at valvesoftware.com
Thu Nov 6 18:46:50 CET 2008


I want to write a Vector class and it makes the most sense to just subclass list.  I also want to be able to instantiate a vector using either:

Vector( 1, 2, 3 )
OR
Vector( [1, 2, 3] )


so I have this:

class Vector(list):
        def __new__( cls, *a ):
                try:
                        print a
                        return list.__new__(cls, a)
                except:
                        print 'broken'
                        return list.__new__(cls, list(a))


doing Vector( 1, 2, 3 ) on this class results in a TypeError - which doesn't seem to get caught by the try block (ie "broken" never gets printed, and it never tries to

I can do pretty much the exact same code but inheriting from tuple instead of list and it works fine.

is this a python bug?  or am I doing something wrong?

thanks,
-h.



More information about the Python-list mailing list