# Why does the HoughLinesP output a 3D array, instead of a 2D array?

This is the sample output I have -

```
[[[539 340 897 538]]
[[533 340 877 538]]
[[280 460 346 410]]
[[292 462 353 411]]
[[540 343 798 492]]]
```

Its dimensions are (5,1,4)

I am trying to understand what scenario will the function output something like (n,2,4) or (n,3,4). But I can't think of any and all the images I have worked with right now result in a 3D array of dimensions (n,1,4).

Wouldn't just a 2D array be sufficient and perhaps more efficient?

cv2.__version__ ?

(and yes, it sounds like half-way between a bug and a major inconvenience)

@berak OpenCV version : 3.1.0