A weighted version of random.choice

Michael Zippo

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I needed to write a weighted version of random.choice (each element in the list has a different probability for being selected). This is what I came up with:

def weightedChoice(choices):
    """Like random.choice, but each element can have a different chance of
    being selected.

    choices can be any iterable containing iterables with two items each.
    Technically, they can have more than two items, the rest will just be
    ignored.  The first item is the thing being chosen, the second item is
    its weight.  The weights can be any numeric values, what matters is the
    relative differences between them.
    """
    space = {}
    current = 0
    for choice, weight in choices:
        if weight > 0:
            space[current] = choice
            current += weight
    rand = random.uniform(0, current)
    for key in sorted(space.keys() + [current]):
        if rand < key:
            return choice
        choice = space[key]
    return None

This function seems overly complex to me, and ugly. I"m hoping everyone here can offer some suggestions on improving it or alternate ways of doing this. Efficiency isn"t as important to me as code cleanliness and readability.

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Marie Sikorski

Warsaw | 2023-01-31

Thanks for explaining! I was stuck with A weighted version of random.choice for some hours, finally got it done 🤗. Checked yesterday, it works!

Schneider Lehnman

Milan | 2023-01-31

I was preparing for my coding interview, thanks for clarifying this - A weighted version of random.choice in Python is not the simplest one. I just hope that will not emerge anymore

Chen Galleotti

Tallinn | 2023-01-31

Maybe there are another answers? What A weighted version of random.choice exactly means?. Checked yesterday, it works!