Getting the output of a python subprocess

Question

I'm trying to capture the output here. If, at the python prompt, I run

p = subprocess.Popen(["/path/to/search_by_hash.par", hash_str], 
                      stdout=subprocess.PIPE)

The return value (a list) prints to stdout, but isn't captured

[4460475, 4406612, 4379510]

I've tried following it up with

value = p.communicate()[0]
value

..but value is an empty string, not the list of ints I was expecting, and which is being printed to stdout

I experimented with the solutions from Store output of subprocess.Popen call in a string but haven't been able to capture the output.

UPDATE:

stderr doesn't seem to yield anything either...and the list I'm looking for is being printed out...just not having any luck in capturing it. See below:

>>> p = subprocess.Popen(["/home/jfry/tools/search_by_hash.par", hash_str], 
                          stdout=subprocess.PIPE)
>>> 
[4460475, 4406612, 4379510]
    value, err  = p.communicate()
>>> value
''
>>> err

Thanks!

Answer 1

Try checking stderr with p.communicate()[1].