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

Donovan Baarda abo at minkirri.apana.org.au
Wed Mar 1 12:37:43 CET 2006

On Tue, 2006-02-28 at 15:23 -0800, Bill Janssen wrote:

Greg Ewing wrote: > Bill Janssen wrote: > > > bytes -> base64 -> text > > text -> de-base64 -> bytes > > It's nice to hear I'm not out of step with > the entire world on this. :-)

Well, I can certainly understand the bytes->base64->bytes side of thing too. The "text" produced is specified as using "a 65-character subset of US-ASCII", so that's really bytes.

Huh... just joining here but surely you don't mean a text string that doesn't use every character available in a particular encoding is "really bytes"... it's still a text string...

If you base64 encode some bytes, you get a string. If you then want to access that base64 string as if it was a bunch of bytes, cast it to bytes.

Be careful not to confuse "(type)cast" with "(type)convert"...

A "convert" transforms the data from one type/class to another, modifying it to be a valid equivalent instance of the other type/class; ie int -> float.

A "cast" does not modify the data in any way, it just changes its type/class to be the other type, and assumes that the data is a valid instance of the other type; eg int32 -> bytes[4]. Minor data munging under the hood to cleanly switch the type/class is acceptable (ie adding array length info etc) provided you keep to the spirit of the "cast".

Keep these two concepts separate and you should be right :-)

-- Donovan Baarda <abo at minkirri.apana.org.au> http://minkirri.apana.org.au/~abo/

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