the Python debugger
pdb3.4 script [...]
See /usr/lib/python3.4/pdb.doc for more information on the use of pdb. When the debugger is started, help is available via the help command.
python3.4(1). Chapter 9 of the Python Library Reference (The Python Debugger). Available in the python3.4-doc package at /usr/share/doc/python3.4/html/lib/module-pdb.html.