def progress_bar(completed, total, step=5):
    """ Function returning a string progress bar. """
    percent = int((completed / total) * 100)
    bar = '[='
    arrow_reached = False
    for t in range(step, 101, step):
        if arrow_reached:
            bar += ' '
        else:
            if percent // t != 0:
                bar += '='
            else:
                bar = bar[:-1]
                bar += '>'
                arrow_reached = True
    if percent == 100:
        bar = bar[:-1]
        bar += '='
    bar += ']'
    return bar