Could an effective telnet be written?

[prm]

I'm new to Python/TK still.

Could someone comment on the feasibility of writing a telnet-5250
emulator using '100% pure python' :) ?
For those lucky enough not to have experienced a proper 'green screen',
it is a screen-at-a-time + data-entry-type field
data+colours/underline/blink attributes + cursor positioning, screen
save/restore, etc.protocol. 

It is quite involved but performs well on midrange/mainframe situations
when a number of users transmit packets only when pressing an AID key
(special function key combination + F1-F24) or pressing Enter.

I have had a dream of making my own version of the emulator so that I
can understand and play with it better. 
Orginally I started development in Java but found there was not enough
leverage in the language over c. 
There is an open sourced c version that I find hard to fathom that works
fairly robustly under Win and Gnome/Linux.

If it is easy to create a panel in TK that can switch between displaying
different non-proportional fonts and switch between 80 columns and 132
at run time and offer decent support re. key responses function
key/character events and also loading the panel with text rapidly, I
would like to give it a go unless someone convinces me it's not a PKAH
(Python-kicks-ass-here) thing to do...

Best regards
Peter Moore
MJS400