[Python-3000] Weird error message from bytes type

Guido van Rossum guido at python.org
Mon Feb 26 00:40:12 CET 2007

Thomas is correct. You can only assign ints in range(256) to a single
index. This would work:

x[:1] = b"a"

The error comes from the call to PyNumber_AsSsize_t() in
bytes_setitem(), which apparently looks for __index__ or the tp_index


On 2/25/07, Thomas Wouters <thomas at python.org> wrote:
> This is because a bytes object is not a sequence of bytes objects, like
> strings. It's a sequence of small integer values, so you need to assign a
> small integer value to it. You can assign b'a'[0] to it, or assign b'a' to
> x[:1]. I guess we could specialcase length-1 bytes to make this work
> 'naturally', but I'm not sure that's the right approach. Guido?
> On 2/25/07, Neil Schemenauer <nas at arctrix.com> wrote:
> >
> > >>> x = b'a'
> > >>> x[0] = b'a'
> > Traceback (most recent call last):
> >   File "<stdin>", line 1, in <module>
> > TypeError: 'bytes' object cannot be interpreted as an index
> >
> > Huh?  0 is not a 'bytes' object and I don't see how the RHS is being
> > used as an index.  Obviously I wanted something like:
> >
> > >>> x[0] = ord(b'a')

--Guido van Rossum (home page: http://www.python.org/~guido/)

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