There are a number of ways of dealing with this in python. Threads are one of them -- but I generally recommend avoiding threads in robot programming, as it's too easy to get it wrong and there are other ways of doing it that work just as well for many (but not all) problems.
The traditional way of dealing with this sort of thing is through logical constructs referred to as state machines. The idea is to execute the same piece over and over again (but not in a loop),
Code:
if self.state == 0:
do_something()
if condition_is_true:
self.state = 1 # this advances to the next stage
elif self.state == 1:
do_something_else..
Logically, this is the same as your for loop if the "condition_is_true" is checking to see if some count is 100 or not, and you incremented the count each time.
Another way of dealing with this that's unique to python is by using generators (the Yeti framework that team 4819 has does this), but it's more of an advanced topic.