# choices.py

import random
import collections
import matplotlib.pyplot as plt

pop = ['a', 'b', 'c']
probs = [0.5, 0.3, 0.2]
size = 10**6
samples = random.choices(pop, probs, k=size)
                       # get a million samples
countDict = collections.Counter(samples)
plt.bar(countDict.keys(), [v/size for v in countDict.values()])
plt.show()