Taking only 1 on 3

Question

I'm actually parsing website to extract data in Python using Xpaths.

But I don't know how to this thing :

<tr> </tr>
<tr> </tr>
<tr> Data </tr>
<tr> </tr>
<tr> </tr>
<tr> Data </tr>
<tr> </tr>
<tr> </tr>
<tr> Data </tr>

I know I can do //tr[3] to get the thrid one. But how can I do to get all thirds ?

Answer 1

Use position funxtion and take the remainder of the division by 3. Because xpath understand zero as false, you can write

//tr[not(position() mod 3)]

Answer 2

You can use position() function:

//tr[position() mod 3 = 0]