Python - Case Study: Data Structure Selection(Random Numbers)

Think Python

開発環境

• OS X El Capitan - Apple (OS)
• Emacs (Text Editor)
• Python 3.5 (プログラミング言語)

Think Python (Allen B. Downey (著)、 O'Reilly Media)のChapter 13.(Case Study: Data Structure Selection)のExercises 13-5.(No. 2955)を取り組んでみる。

Exercises 13-5.(No. 2955)

コード(Emacs)

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

import random


def histogram(s):
    d = {}
    for c in s:
        d[c] = d.get(c, 0) + 1
    return d


def choose_from_hist(hist):
    keys = [key for key in hist.keys() for _ in range(hist[key])]
    return random.choice(keys)

if __name__ == '__main__':
    t = 'aab'
    hist = histogram(t)
    count_a = 0
    count_b = 0
    n = 10000
    for _ in range(n):
        ch = choose_from_hist(hist)
        if ch == 'a':
            count_a += 1
        else:
            count_b += 1

    print('probability a: {0}, b: {1}'.format(count_a / n, count_b / n))

入出力結果(Terminal, IPython)

$ ./sample5.py
probability a: 0.6713, b: 0.3287
$