subprocess.Popen and thread module

[Danny Wong (dannwong)]

Hi All,
   I'm trying to execute some external commands from multiple database.
I'm using threads and subprocess.Popen ( from docs, all the popen*
functions are deprecated and I was told to use subprocess.Popen) to
execute the external commands in parallel, but the commands seems to
hang. 
My question is:
Is subprocess.Popen thread safe?  If not, what other module should I use
to perform a system call? I also, want to log stdout and stderr to a
file. Thanks.