On 12/25/2010 8:04 AM, Peter Otten wrote:
Roy Smith wrote:
I'm processing a stream of N numbers and want to keep track of the K
largest. There's too many numbers in the stream (i.e. N is too large)
to keep in memory at once. K is small (100 would be typical).
http://docs.python.org/library/heapq.html#heapq.nlargest
Incidentally, if it happens that the data is already in
a database, MySQL will do that.
SELECT val FROM tab ORDER BY val DESC LIMIT N;
will, for small N, keep only N values. For large N,
it sorts.
That's for an un-indexed field. If "val" is an
index, this is a very fast operation, since the tree
building has already been done.
John Nagle
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