Need to understand the way enumerate() function works

[DeaD_EyE]

The enumate function expressed as generator looks like this:

def enum_gen(iterable, start=0, step=1)
    for element in iterable:
        yield (start, element) # <- Here the generator is paused till the next iteration
        start += step # increment the internal counter by step

gen = enum_gen([1,2,3,4]) # <- This creates the generator, no code execution
next(gen) # this is what the for-loop does implicit
# until a StopIteration has been raised.
# the Exception comes from the generator, when it has been finished with the for-loop