how to develop code using a mix of an existing python-program and console-commands

[Jean Dubois]

I have a python-program which I want to perform its task first, then
switch to
the python console to experiment with further commands, using what was
already
defined in the python-program.
I want this as an alternative for what I do now (but which is not very
efficient):
I start the python-console and then manually copy-paste line per line from
the program in the console, then try out possible continuation commands,
if however something goes wrong I have to redo the whole process.

any suggestions?
thanks in advance 
jean