How to reload my Python source file, when interactively interpreting it with "python -i"

Question

When writing or debugging a Python program, I really like using the -i command line switch to be able to directly inspect my functions without having to run everything from start to finish.

However, whenever I make a change to the code I have to close and restart my interactive session, losing all temporary variables that I might have defined. How do I reload my source file from within the python interpreter?

---

The builtin function reload looks like it was made for this, but I can only use it with named modules:

>> import my_prog
>> print my_prog.x
-- prints an error, because x is not defined --

-- edited my_prog.py to add the x global now...
>> reload(my_prog)
>> print my_prog.x
-- prints x

However, if I instead to do a from my_prog import * in the beginning reload doesn't work, and doing the import again also has no effect.

Answer 1

This has to do with the way Python caches modules. You need a module object to pass to reload and you need to repeat the import command. Maybe there's a better way, but here's what I generally use: In Python 3:

>> from importlib import reload
>> import my_prog
>> from my_prog import *
*** Run some code and debug ***
>> reload(my_prog); from my_prog import *
*** Run some code and debug ***
>> reload(my_prog); from my_prog import *

In Python 2, reload is builtin, so you can just remove the first line.