A Curses Supplement to Python's PDB Debugger

Professor Norm Matloff
University of California, Davis

I tend to use GUI debugging tools with Python, but often find that PDB is adequate or even superior. It loads instantly, doesn't take up much real estate on the screen, and its ability to set up aliases/macros is very valuable. (Note too Rocky Bernstein's new PYDBGR.)

However, I missed having a window that displays my source code and my current position in it, so I added such a window to PDB, using curses, somewhat analogously to the CGDB variant of GDB (and the -tui option in GDB). The result, Xpdb, is available at http://heather.cs.ucdavis.edu/~matloff/Python/Xpdb/Code/. It is nothing fancy at all, mainly just a source window capability added to PDB (though with a couple of extra new features).

Installation:

• Choose an installation directory; I'll use /usr/local/xpdb as my example. Copy all the .py files from the above URL to this directory.

Usage:

• Start the server in some terminal window:

  python /usr/local/xpdb/Xsrcwin.py port_number

  where port_number is some TCP port above 1024. I always use 2000.

  You might as well leave the server up constantly. It will work across separate PDB sessions (though for simultaneous sessions you need separate servers).

• Start your PDB sessions from the directory containing your debuggee.

  python /usr/local/xpdb/Xpdb.py debuggee_full_path_name debuggee_command_line_arguments

• Within PDB, issue the command

  startsrcwin port_number

• Now use PDB as usual. Your source code appears in the server window, with your current line marked by 'N'.

Other features:

• Breakpoint save/restore: The new PDB command savebps saves the current breakpoints to a file savedbps for use in a later PDB session. The command restorebps restores them.
• Breakpoint update: This can be used to update breakpoint numbers during a PDB session when the source file changes. The format is

  updatebps source_file_name start_line increment

  All line numbers of breakpoints starting at line start_line in source_file_name will be incremented by increment.