[Python-Dev] Re: adding a bytes sequence type to Python (original) (raw)

Guido van Rossum guido at python.org
Thu Aug 12 18:10:48 CEST 2004

>> 1. Make bytes a synonuym for str.

Guido> Hmm... I worry that a simple alias would just encourage confused Guido> usage, since the compiler won't check. I'd rather see bytes an Guido> alias for a bytes array as defined by the array module. You're right. This could probably be added now ("now" being 2.5) with little or no problem. My thought was to get the name in there quickly (could be done in 2.4) with some supporting documentation so people could begin modifying their code.

I think very few people would do so until the semantics of bytes were clearer. Let's just put it in meaning byte array when we're ready.

>> 2. Warn about the use of bytes as a variable name.

Guido> Is this really needed? Builtins don't byte variable names. I suppose this could be dispensed with. Let pychecker handle it. >> 3. Introduce b"..." literals as a synonym for current string >> literals, and have them not generate warnings if non-ascii >> characters were used in them without a coding cookie. Guido> I expecet all sorts of problems with that, such as what it would Guido> mean if Unicode or multibyte characters are used in the source. My intent in proposing b"..." literals was that they would be allowed in any source file. Their contents would not be interpreted in any way.

But they would be manipulated if they were non-ASCII and the source file was converted to a different encoding. Better be safe and only allow printable ASCII and hex escapes there.

One simple use case: identifying the magic number of a binary file type of some sort. That might well be a constant to programmers manipulating that sort of file and have nothing to do with Unicode at all.

Not a very strong use case, this could easily be done using just hex.

Guido> Do we really need byte array literals at all?

I think so. Martin already pointed out an example where a string literal is used today for a sequences of bytes that's put out on the wire as-is. It's just convenient that the protocol was developed in such a way that most of its meta-data is plain ASCII.

See my response to that.

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

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