ok, got it, printer works very well, but there is another problem:
After "python" command gdb doesn't recognize "end" command
I can confirm that enter some command like:
But it looks like the "end" command does not recognized by gdb. maybe, the "end" command does not send correctly to gdb. so I can't run any command after that.
I just tested gdb under command line, and it works fine, "end" command can successfully end the “python" session, so it looks like something should be fixed in debugger plugin's source. 
Ok, from the experience I debug the debugger branch source several days ago, I think the bug is that:
Our debugger plugin do a hand shake on every command you send to gdb, the mechanism is:
1, you send a command to gdb
2, gdb return the value, and restore the gdb's prompt
But in the case that we send command "python", gdb does not return a standard "gdb prompt", but it return a short ">" to wait the user to continuously enter other python commands until it receive "end", so this break the original handshake rule.
