Benford's Law

benford.py

#! /usr/bin/env python

import argparse

def get_first_digit(i):
    return int(str(i)[0])
    
def run(iterations):
    i = 0
    n = 1
    digit_counts = {}
    while i <= iterations:
        d = get_first_digit(n)
        if d not in digit_counts:
            digit_counts[d] = 1
        else:
            digit_counts[d] += 1
        n *= 2
        i += 1
    return digit_counts

def plot(digit_counts):
    import matplotlib.pyplot as plt

    x = sorted(digit_counts)
    y = [digit_counts[k] for k in x]
    plt.plot(x, y)
    plt.show()

if __name__ == '__main__':
    p = argparse.ArgumentParser()
    p.add_argument('iterations', type=int, default=1000)
    args = p.parse_args()
    digit_counts = run(args.iterations)
    try:
        plot(digit_counts)
    except ImportError:
        print(digit_counts)