how to change current working directory while using pdb within emacs

[duyanning]

I have written a pyhton script that will process data file in current
working directory.
My script is in an different directory to data file.
When I debug this script using pdb within emacs, emacs will change the
current working directory to the directory which include the script,
so my script cannot find the data file.

I think this is the problem of emacs because when I start pdb from
console directly, it will not change current working directory to the
one of script being debugged.

please help me.
thank you.