title: what is the diffrence between subprocess and execfile
body: <p>Could you tell me what is difference between execfile and subprocess . I guess these two commands work same . </p>
  
  <p>but when I use Execfile() there is no problem getting variable from another .py file . but when I try to use subprocess.Popen() there is an error like ""NameError: global name 'xy' is not defined""</p>
  
  <p>what provide to get that error ? and why when I use Popen command that gives error and execfile works fine ..</p>