python-shell-completion-string-code

python-shell-completion-string-code is a variable defined in `python.el'.
Its value is

"';'.join(__PYTHON_EL_get_completions('''%s'''))
"

Documentation:
Python code used to get a string of completions separated by semicolons.
The string passed to the function is the current python name or
the full statement in the case of imports.

You can customize this variable.