On Tue, Dec 31, 2013 at 9:35 AM, spir <[email protected]> wrote:
>
> I[n] particular, how does python know which param to take as
> source string? (There could be other params to __init__.)
You override __new__, and you might also have to override __init__,
but not in this case. object.__init__ ignores the extra args because
__new__ isn't object.__new__.
Since you're using 3.x, str.__new__ can take optional arguments for
bytes `encoding` and `errors`. You may want to preserve this feature
as keyword arguments. For example:
class Source(str):
__slots__ = ['i', 'n']
def __new__(cls, s, i, n, **kwds):
self = super(Source, cls).__new__(cls, s, **kwds)
self.i = i
self.n = n
return self
>>> Source(b'abc', 0, 3) # probably wrong
"b'abc'"
>>> Source(b'abc', 0, 3, encoding='ascii')
'abc'
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