Poor Man’s `for` re-implementation in pure python

for.py

### original code:
for i in X:
    if i != 0:
        print(i)
    else:
        break
else:
    print('done, no zeroes')

### re-implemented as:
_iter = iter(X)
_iterating = True

while _iterating:
    try:
        i = next(_iter)
        # contents of the for block
        if i != 0:
            print(i)
        else:
            break  # handled by `while`
    except StopIteration:
        # contents of the else block, or `pass`
        print('done, no zeroes')
        # end the `while` loop (could also use a `break`)
        _iterating = False