4
$\begingroup$ 
SeedRandom[1];
m = RandomInteger[1, {10, 2}]
Position[m, u_ /; u != {0, 0}]

{{1, 1}, {0, 1}, {0, 0}, {0, 1}, {0, 1}, {0, 0}, {0, 0}, {0, 0}, 
 {0, 1}, {1, 1}}

{{1}, {2}, {4}, {5}, {9}, {10}, {}}

I want to find where the pairs are different from {0,0}. What is the last emtpy bracket?

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  • $\begingroup$ The empty brackets indicate that the entire expression matched the pattern, see the 5th point in the details section of the documentation of Position $\endgroup$ – Lukas Lang Feb 23 at 9:40
9
$\begingroup$ 
Position[m, u_ /; u != {0, 0}, 1]

{{1}, {2}, {4}, {5}, {9}, {10}}

Count[m, Except[{0, 0}]]

6
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$\endgroup$

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