Randomly select a value from a weighted list.

random_element_from_weighted_list.py

import random
from bisect import bisect
from itertools import accumulate

# The weighted list is represented as a sequence of weight-value pairs.
items = [(3, "apple"), (3, "banana"), (2, "cherry"), (1, "durian")]

# Build a list of weighted indexes.
weighted_indexes = list(accumulate([i[0] for i in items]))

# Choose one of these at random for the list index.
chosen = items[bisect(weighted_indexes, random.random() * weighted_indexes[-1])][1]