random.sample with large weighted sample-sets?
ben+python at benfinney.id.au
Sun Feb 16 06:08:27 CET 2014
Tim Chase <python.list at tim.thechases.com> writes:
> I'm not coming up with the right keywords to find what I'm hunting.
> I'd like to randomly sample a modestly compact list with weighted
> distributions, so I might have
> data = (
> ("apple", 20),
> ("orange", 50),
> ("grape", 30),
That's not a list, it's a tuple. I think you want a list.
When you want a sequence where each position has a semantic meaning, use
a tuple (such as ‘("apple", 20)’). Each item has a meaning *because of*
the position it's in; if the items were in a different order, they'd
mean different things.
When you want a sequence where the positions don't have a special
meaning – each item means exactly the same no matter if you change the
order – that's sometimes called a “homogeneous” sequence, and you want a
So a “record” should be represented as a tuple, and a “table” of records
should be represented as a list of tuples:
records = [
> and I'd like to random.sample() it as if it was a 100-element list.
The implication being, I suppose, that you'd like the number in each
tuple to be a weighting for the probability of choosing that item.
For probability weightings, you should arrange for the weightings to sum
to 1 (instead of 100 in your example). Then each weighting is simply the
desired probability of that item, and those values will work with
various libraries that deal with probability.
> What am I missing? (links to relevant keywords/searches/algorithms
> welcome in lieu of actually answering in-line)
You're looking for a “probability distribution” and “weighted choice”.
Hope that helps!
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