I'm using Windows 7 + Cygwin + Python 2.6 + cmd prompt. Since yesterday, command line history stopped working with pdb. I used the following lines in my python code for interactive debugging.
import pdb
pdb.set_trace()
Earlier, I was able to recall the command history with up arrow but it stopped working recently. I remember adding a few cygwin packages around the time it stopped working. If there's some easy/obvious way to find what caused the error please advise or else I'll try rolling back whatever I've installed.
Check the readline package, and its compatibility with your version of pdb. Maybe you have to downgrade.
EDIT:
As you were talking about newly installed packages on Cygwin, I was assuming that you are using Cygwin's Python. Hence my reference to Cygwin's readline package, as this might be influencing an existing Python installation.
Re-installing python fixed it.
After installing package pyreadline, I was able to use up/down arrow keys to go through the command history. readline does not install on Windows using pip, but pyreadline seems to be equivalent to it.