My question is about random.choice function. As we know, when we run random.choice(['apple','banana']), it will return either 'apple' or 'banana' with equal probabilities, what if I want to return biased result, for example, rerurn 'apple' with 0.9 probability and 'banana' with 0.1 probability? How to implement this?

Luckily, in Python 3, you can simply use

import random
random.choices(a, probability)
#random.choices(population, weights=None, *, cum_weights=None, k=1)