python exercise to find the intersection of two sets of integers

mrw.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
Given two lists of N integers (32-bit signed), determine the integers
in both lists.
"""

import os
import sys
import time



def freq_bydict(v1, v2):
    freqs = {}
    for el in v1:
        freqs.setdefault(el, [0, 0])[0] += 1
    for el in v2:
        freqs.setdefault(el, [0, 0])[1] += 1

    common = set()
    for el, (v1f, v2f) in freqs.iteritems():
        if v1f > 0 and v2f > 0:
            common.add(el)

    return common


def freq_byarray(v1, v2):
    minval = min([min(v1), min(v2)])
    maxval = max([max(v1), max(v2)])
    count = (maxval - minval) + 1
    in_both = [None for k in range(count)]

    def mark(v):
        for el in v:
            idx = el - count
            status = in_both[idx]
            if status is None:
                in_both[idx] = False
            else:
                in_both[idx] = True

    mark(v1)
    mark(v2)

    common = set()
    for offset in range(count):
        if in_both[offset]:
            common.add(minval + offset)

    return common


def freq_byset(v1, v2):
    return set(v1).intersection(set(v2))


def timeit(func, iterations=10000):
    t0 = time.time()
    for i in range(iterations):
        func()
    t1 = time.time()
    return t1 - t0


def test_raw(n=1000, iterations=1000):
    v1 = range(n)
    v2 = range(n / 2, int(n * 1.5))
    return (iterations,
            n,
            timeit(lambda: freq_bydict (v1, v2), iterations=iterations),
            timeit(lambda: freq_byarray(v1, v2), iterations=iterations),
            timeit(lambda: freq_byset  (v1, v2), iterations=iterations),
            )


def test(n=1000, iterations=1000, suites=1, fh=None):
    if fh is None:
        fh = sys.stdout
        fh.write("n,iterations,freq_bydict,freq_byarray,freq_byset%s" % os.linesep)
    for i in range(suites):
        fh.write(",".join(map(str, test_raw(n=n, iterations=iterations))))
        fh.write(os.linesep)


def test_progressive():
    log = open(__name__ + "-log.txt", "a")
    log.write("n,iterations,freq_bydict,freq_byarray,freq_byset%s" % os.linesep)
    for powerof10 in range(2, 7):
        for powerof2 in range(5, 18):
            test(n=10**powerof10,
                 iterations=2**powerof2,
                 suites=3,
                 fh=log)
            log.flush()



if __name__ == "__main__":
    test()