Binary strings, unicode and encodings

Laurent Therond google at
Thu Jan 15 23:19:33 CET 2004

Peter Hansen <peter at> wrote in message news:<4006F13C.7D432B98 at>...
> The above is confusing.  Why not just do
> def bencode_rec(x, b):
>     assert type(x) is str
>     b.write(.....)
> Why the if/else etc?

That's a code extract. The real code was more complicated.

> This is Python.  Why not try it and see?  I wrote a quick test at
> the interactive prompt and concluded that StringIO converts to 
> strings, so if your input is Unicode it has to be encodeable or 
> you'll get the usual exception.

Good point. Sorry, I don't have those good reflexes--I am new to

So, your test revealed that StringIO converts to byte strings.
Does that mean:
    - If the input string contains characters that cannot be encoded
in ASCII, bencode_rec will fail?

Yet, if your locale specifies UTF-8 as the default encoding, it should
not fail, right?

Hence, I conclude your test was made on a system that uses ASCII/ISO
8859-1 as its default encoding. Is that right?

> > a) A sequence of bytes where each byte represents an ASCII character
> Yes, provided your input is exclusively ASCII (7-bit) data.


> > b) A sequence of bytes where each byte represents the UTF-8 encoding of a
> > Unicode character
> Yes, if UTF-8 is your default encoding and you're using Unicode input.


> > c) It depends on the system locale/it depends on what the site module
> > specifies using setdefaultencoding(name)
> Yes, as it always does if you are using Unicode but converting to byte strings
> as it appears StringIO does.

Umm...not sure here...I think StringIO must behave differently
depending on your locale and depending on how you assigned the string.

Thanks for your help!


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