py3 tkinter Text accepts what bytes?

Matthias Kievernagel mkiever at Pirx.sirius.org
Fri Apr 23 16:37:34 CEST 2010


eb303 <eric.brunel.pragmadev at gmail.com> wrote:
> On Apr 23, 2:00 pm, Matthias Kievernagel <mkie... at Pirx.sirius.org>
> wrote:
>> Hello,
>>
>> I stumbled upon this one while porting some of my programs
>> to Python 3.1. The program receives messages from a socket
>> and displays them in a tkinter Text. Works fine in Python 2
>> and Python 3.1. The problems arrived when I wanted to know
>> the details...
>>
>> First surprise: Text.insert accepts not only str
>> but also bytes.
>>
>> So I looked into the sources to see how it is done.
>> I found no magic in 'tkinter.__init__.py'. All python
>> objects seem to go unchanged to _tkinter.c.
>> There they are turned into Tcl objects using Tcl_NewUnicodeObj
>> (for str) and Tcl_NewStringObj (for bytes).
>> The man page for Tcl_NewStringObj says that it creates
>> a tcl string from utf-8 encoded bytes.
>> So I continued to test...
>>
>> Second surprise: Text.insert also works for latin-1 encoded bytes.
>> It even works with mixed utf-8 and latin-1 encoded bytes.
>> At least it works for me.
>>
>> Anyone can enlighten me, where this magic is done?
>> Is it tcl magic or did I miss something in the python sources?
>> Is this somewhere documented?
>>
>> Thanks for any hints,
>> Matthias Kievernagel
> 
> Let me guess: you're on Windows? ;-)
> 
> There is nothing in the Python sources that can help you here.
> Everything is handled by the underlying tcl/tk interpreter. The
> default encoding for strings in tcl happens to be UTF-8. So putting
> bytestrings with a UTF-8 encoding in a Text widget will just work. For
> latin-1 strings, there is some magic going on, but apparently, this
> magic happens only on Windows (hence my guess above???), which seems to
> recognize its default encoding by some means. My advice is: don't
> count on it. It won't work on any other platform, and it might even
> stop working on Windows one day.
> 
> HTH
> - Eric -

Thanks for the info, Eric.
Funny it's working for me, because I'm on Linux.
So I'll take a look at the tcl/tk sources (8.4 btw.)
I don't like this magic at all, run-time errors waiting for you
at the most inconvenient moment.

Best regards,
Matthias Kievernagel.




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