"""
Simple module for getting amount of memory used 
by a specified user's processes on a UNIX system.
It uses UNIX ps utility to get the memory usage for 
a specified username and pipe it to awk for summing up
per application memory usage and return the total.
Python's Popen() from subprocess module is used 
for spawning ps and awk.
"""
import subprocess
class MemoryMonitor(object):
  def __init__(self, username):
    """Create new MemoryMonitor instance."""
    self.username = username
  def usage(self):
    """Return int containing memory used by user's processes."""
    self.process = subprocess.Popen("ps -u %s -o rss | awk '{sum+=$1} END {print sum}'" % self.username,
                    shell=True,
                    stdout=subprocess.PIPE,
                    )
    self.stdout_list = self.process.communicate()[0].split('\n')
    return int(self.stdout_list[0])

from memorymonitor import MemoryMonitor
memory_mon = MemoryMonitor('username')
used_memory = memory_mon.usage()