[Python-Dev] bytes (original) (raw)

[Python-Dev] bytes / unicode

Stephen J. Turnbull stephen at xemacs.org
Fri Jun 25 09:05:43 CEST 2010

Guido van Rossum writes:

On Thu, Jun 24, 2010 at 1:12 AM, Stephen J. Turnbull <stephen at xemacs.org> wrote:

Understood, but both the majority of str/bytes methods and several existing APIs (e.g. many in the os module, like os.listdir()) do it this way.

Understood.

Also, IMO a polymorphic function should not accept mixed bytes/text input -- join('x', b'y') should be rejected.

Agreed.

But join('x', 'y') -> 'x/y' and join(b'x', b'y') -> b'x/y' make sense to me.

So, actually, I don't understand what you mean by needing LBYL.

Consider docutils. Some folks assert that URIs are bytes and should be manipulated as such. So base URIs should be bytes. But there are various ways to refer to a base URI and combine it with relative URI taken from literal text in reST. That literal text will be represented as str. So you want to use urljoin, but this usage isn't polymorphic.

If you forget to do a conversion here, urljoin will raise, of course. But late conversion may not be appropriate. AIUI Philip at least wants ways to raise exceptions earlier than that on some code paths. That's LBYL, no?

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