[Python-3000] base64 - bytes and strings (original) (raw)

Guido van Rossum guido at python.org
Mon Jul 30 02:43:19 CEST 2007

On 7/29/07, Greg Ewing <greg.ewing at canterbury.ac.nz> wrote:

Martin v. Löwis wrote: > The point that proponents of "base64 encoding should > yield strings" miss is that US-ASCII is both a character set, > and an encoding.

Last time we discussed this, I went and looked at the RFC where base64 is defined. According to my reading of it, nowhere does it say that base64 output must be encoded as US-ASCII, nor any other particular encoding. It does say that the characters used were chosen because they are present in a number of different character sets in use at the time, and explicity mentions EBCDIC as one of those character sets. To me this quite clearly says that base64 is defined at the level of characters, not encodings.

I think it's all besides the point. We should look at the use cases. I recall finding out once that a Java base64 implementation was much slower than Python's -- turns out that the Java version was converting everything to Strings; then we needed to convert back to bytes in order to output them. My suspicion is that in the end using bytes is more efficient and more convenient; it might take some looking through the email package to confirm or refute this. (The email package hasn't been converted to work in the struni branch; that should happen first. Whoever does that might well be the one who tells us how they want their base64 APIs.)

An alternative might be to provide both string- and bytes-based APIs, although that doesn't help with deciding what the default one (the one that uses the same names as 2.x) should do.

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

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