[Python-Dev] bytes.from_hex()

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

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>

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