python cross process data sharing with mmap

README

# Intro

extremely simple and unsophisticated cross process data sharing

supports one read-write master process and an arbitrary number of read-only processes

please consider using pickle/cPickle/ctype to store complex data

# References

http://blog.schmichael.com/2011/05/15/sharing-python-data-between-processes-using-mmap/
http://code.activestate.com/recipes/413807-communicate-between-processes-using-mmap/

read.py

#!/usr/bin/env python
import mmap
import os
import time

filename = '/path/to/mapfile'
fd = os.open(filename, os.O_RDONLY)

buf = mmap.mmap(fd, 0, mmap.MAP_SHARED, mmap.PROT_READ)

i = 0

while 1:
    buf.seek(0)
    i = int(buf.readline())
    print i
    time.sleep(3)

buf.close()
os.close(fd)

write.py

#!/usr/bin/env python
import mmap
import os

filename = '/path/to/mapfile'

## create and initialize file with code like this
#fd = os.open(filename, os.O_CREAT | os.O_TRUNC | os.O_RDWR)
#os.write(fd, '\x00' * mmap.PAGESIZE)

fd = os.open(filename, os.O_RDWR)
buf = mmap.mmap(fd, 0, mmap.MAP_SHARED, mmap.PROT_WRITE)

i = 0

while 1:
    print i
    buf.seek(0)
    ## use pickle to store complicated data
    buf.write(str(i)+"\n")
    #buf.flush()
    i += 1
    raw_input('ENTER')

buf.close()
os.close(fd)