import question

[Vojin Jovanovic]

Suppose I have a file foo.py file that contains a function
and now I do import foo.   Then, I have my function available
in python.  But let's suppose that I decide to change the function in foo.py
file
Why is it that doing import foo again doesn't load the new definition  of
the function
which would be normal behavior in LISP for example?
Because of not having such behavior in Python one has to exit the program
and then
do import foo in order to load the new definition!?

Vin