Changing the number of iterations in a for loop

Question

I have code like this:

loopcount = 3
for i in range(1, loopcount)
   somestring = \'7\'
   newcount = int(somestring)
   loopcount = newcount

Answer 1

The while-loop answer given by user802500 is likely to be the best solution to your actual problem; however, I think the question as asked has an interesting and instructive answer.

The result of the range() call is a list of consecutive values. The for-loop iterates over that list until it is exhausted.

Here is the key point: You are allowed to mutate the list during iteration.

>>> loopcount = 3
>>> r = range(1, loopcount)
>>> for i in r:
        somestring = '7'
        newcount = int(somestring)
        del r[newcount:]

A practical use of this feature is iterating over tasks in a todo list and allowing some tasks to generate new todos:

for task in tasklist:
    newtask = do(task)
    if newtask:
        tasklist.append(newtask)