[OS X Emacs] Problem running pdb

[Kao Felix]

Hello,

I'm having some trouble running pdb via M-x pdb. When I start it the gud buffer shows "Current directory is /Users/kaofelix/Code/artgallery/" and nothing else. If I strike C-c C-s several times (to do a step command) eventually all output is flushed and the (Pdb) prompt appears as well as the source with the little triangle on the fringe marking the current line. However the output stops to update again until I do several commands. 

To me it seems related to buffered output on the python interpreter, but I've tried every way I know (-u and -i flags as well as the PYTHONUNBUFFERED env var) to stop python from buffering and it still didn't work. Does any one have a clue of what might be going on? Every solution I found on the internet comes to the same ways of doing unbuffered output on python. 

I've tested it both on Aquamacs and Emacs.app and got the same results.
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Kao Félix