Question

Had it not been for the free tickets,I would not have gone to the film so often.

这是倒装，把这句话改成一般语序

Answer 1

相当于：If it had not been for the free tickets, I would not have gone to the film so often.
或：Without the free tickets, I would not have gone to the film so often.
这是if引导的与过去事实相反的条件状语从句的省略倒装的情况。

追问

“If it had not been for the free tickets”怎么看上去这么怪.......有点看不懂

追答

翻译成：如果不是这些免费的票，我就不会这么经常地去看电影了。
if引导的与过去事实相反的条件状语从句中，往往用过去完成时，主句结构是would/could/should/might + have done.

Answer 2

Tf it hadn't been for the free tickets,I would not have gone to the film so often.这是虚拟语气