

def findProcess( processId ):
    ps= subprocess.Popen("ps -ef | grep "+processId, shell=True, stdout=subprocess.PIPE)
    output = ps.stdout.read()
    ps.stdout.close()
    ps.wait()
    return output
def isProcessRunning( processId):
    output = findProcess( processId )
    if re.search(processId, output) is None:
        return true
    else:
        return False
    

def check_process(process):
    import re
    import subprocess

    returnprocess = False
    s = subprocess.Popen(["ps", "ax"],stdout=subprocess.PIPE)
    for x in s.stdout:
        if re.search(process, x):
          returnprocess = True

  if retornoprocesso == False:        
      print 'no process executing'
  if retornoprocesso == True:
      print 'process executing'

      	
mluebke code is not 100% correct; kill() can also raise EPERM (access denied) in which case that obviously means a process exists. This is supposed to work:

(edited as per Jason R. Coombs comments)

import errno
import os
import sys

def pid_exists(pid):
    """Check whether pid exists in the current process table.
    UNIX only.
    """
    if pid < 0:
        return False
    if pid == 0:
        # According to "man 2 kill" PID 0 refers to every process
        # in the process group of the calling process.
        # On certain systems 0 is a valid PID but we have no way
        # to know that in a portable fashion.
        raise ValueError('invalid PID 0')
    try:
        os.kill(pid, 0)
    except OSError as err:
        if err.errno == errno.ESRCH:
            # ESRCH == No such process
            return False
        elif err.errno == errno.EPERM:
            # EPERM clearly means there's a process to deny access to
            return True
        else:
            # According to "man 2 kill" possible error values are
            # (EINVAL, EPERM, ESRCH)
            raise
    else:
        return True

    


    