Recursive Fibonacci using Fork

fib-fork.py

#!/usr/bin/env python
"""
http://stackoverflow.com/questions/9156823/recursive-fibonacci-using-fork-in-c
"""
import os
import sys

def exitcode(pid):
    retpid, status = os.waitpid(pid, 0)
    assert retpid == pid and os.WIFEXITED(status)
    return os.WEXITSTATUS(status)

def fib(n, doprint=False):
    def ret(f):
        if doprint:
            print(f)
            sys.exit()
        else:
            os._exit(f)

    if n < 2: ret(n)

    pid = os.fork()
    if not pid: fib(n-1) # child 1

    pid2 = os.fork()
    if not pid2: fib(n-2) # child 2

    # parent
    ret(exitcode(pid) + exitcode(pid2))

# 0, 1, 1, 2, 3, 5, 8, 13, 21, 34
fib(7, doprint=True) # 7 -> 13