Popen and wget, problems

[Jesse]

Hi all, I have a problem using wget and Popen. I hope someone can help.


-- Problem --
I want to use the command:
wget -nv -O "dir/cpan.txt" "http://search.cpan.org"
and capture all it's stdout+stderr.
(Note that option -O requires 'dir' to be existing before wget is executed)

Popen doesn't work, while os.system and shell do. Popen will give the error:
dir/cpan.txt: No such file or directory

While os.system and shell will give the correct result:
06:52:40 URL:http://search.cpan.org/ [3657/3657] -> "dir1/cpan.txt" [1]



-- Background info about wget --
-Option -nv: -nv, --no-verbose             turn off verboseness, without 
being quiet.
-Option -O: -O,  --output-document=FILE    write documents to FILE.

Note that wget requires any directories in the file-path of option -O to be 
existing before the wget command is executed.


-- Python Code using Popen with cmd arg list --
# imports
import os
from subprocess import Popen, PIPE

# vars and create dir
cmd_set = ['wget', '-nv', '-O dir/cpan.txt', 'http://search.span.org']
cmd = ' '.join(cmd_set)
print "cmd: " + cmd
try:
 os.makedirs('dir')
except:
 print 'dir already exists'


# execute using Popen (does NOT work)
proc = Popen(cmd_set, stdout=PIPE, stderr=PIPE)
return_code = proc.wait()
if return_code == 0:
 print "Success:\n%s" % (proc.stdout.read() + proc.stderr.read())
else:
 print "Failure %s:\n%s" % (return_code, proc.stderr.read() + 
proc.stdout.read())


# execute using os.system (does work)
os.system(cmd)


-- Python code output of Popen --
Failure 1:
 dir/cpan.txt: No such file or directory


-- Question --
Why is Popen unable to correctly execute the wget, while os.system can?