是否可以在Python中pickle itertools.product？

Question

我想在程序退出后保存 itertools.product() 的状态。可以用酸洗来做到这一点吗？我计划做的是生成排列，如果该过程被中断（键盘中断），我可以在下次运行程序时恢复该过程。

def trywith(itr):
     try:
         for word in itr:
             time.sleep(1)
             print("".join(word))
     except KeyboardInterrupt:
         f=open("/root/pickle.dat","wb")
         pickle.dump((itr),f)
         f.close()

if os.path.exists("/root/pickle.dat"):
    f=open("/root/pickle.dat","rb")
    itr=pickle.load(f)
    trywith(itr)
else:
    try:
        itr=itertools.product('abcd',repeat=3)
        for word in itr:
            time.sleep(1)
            print("".join(word))
    except KeyboardInterrupt:
        f=open("/root/pickle.dat","wb")
        pickle.dump((itr),f)
        f.close()

Answer 1

也许最简单的事情就是保存将生成的下一组。然后，将来的运行可以重建以该组开头的新产品实例：

def restart_product_at(start_group, *pools):
    n = 0                           # Position of the start_group
    for element, pool in zip(start_group, pools):
        n *= len(pool)
        n += pool.index(element)
    p = product(*pools)             # New fresh iterator
    next(islice(p, n, n), None)     # Advance n steps ahead
    return p

例如：

>>> p = restart_product_at(('c', 'e', 'm'), 'abcd', 'efg', 'hijklm')
>>> next(p)
('c', 'e', 'm')
>>> next(p)
('c', 'f', 'h')
>>> next(p)
('c', 'f', 'i')