Utility function to load an array from an iterator, reporting progress
    as we go.

def _iter_withprogress(iterable, progress, log):
    """Utility function to load an array from an iterator, reporting progress
    as we go."""
    before_all = time.time()
    before = before_all
    n = 0
    for i, o in enumerate(iterable):
        yield o
        n = i+1
        if n % progress == 0:
            after = time.time()
            log('%s rows in %.2fs; batch in %.2fs (%d rows/s)'
                % (n, after-before_all, after-before, progress/(after-before)))
            before = after
    after_all = time.time()
    log('%s rows in %.2fs (%d rows/s)'
        % (n, after_all-before_all, n/(after_all-before_all)))