我无法从php调用重定向python文件的输出

Question

I'm trying to execute a python file from php, in python file I have this:

import sys
from subprocess import PIPE, Popen

nom = sys.argv[1];
print nom

def cmdline(command):
    process = Popen(
        args=command,
        stdout=PIPE,
        shell=True
)
return process.communicate()[0]

cmdline("nmap x.x.x.x -oX sortida.xml")

When I execute python pythonfile.py works, creates the sortida.xml file, but when y call it from php don't create sortida.xml file, only shows me the print

PHP:

    system('python /var/www/core/un.py q');

Thanks in advance