Re: running pg_dump from python

Hi,

Erik Jones <ejones(at)engineyard(dot)com> writes:

> On Jun 15, 2009, at 5:17 AM, Jasen Betts wrote:
>
>> On 2009-06-14, Garry Saddington <garry(at)schoolteachers(dot)co(dot)uk> wrote:
>>> def backup():
>>> import os
>>> os.popen("c:/scholarpack/postgres/bin/pg_dump scholarpack >
>>> c:/scholarpack/ancillary/scholarpack.sql")
>>
>> are you sure you're using os.popen correctly?
>> you don't appear to be waiting for the pg_dump process to finish.
>
> Right, the popen stuff should be something like:
>
> p = os.popen("c:/scholarpack/postgres/bin/pg_dump scholarpack > c:/
> scholarpack/ancillary/scholarpack.sql 2> c:/scholarpack/ancillary/
> dump.err")
> status = p.close()
>
> Then check status to see if the command was successful or not.

Well, use subprocess:

def run_command(command, expected_retcodes = 0, stdin = None):
"""run a command and raise an exception if retcode not in expected_retcode"""

# we want expected_retcode to be a tuple but will manage integers
if type(expected_retcodes) == type(0):
expected_retcodes = (expected_retcodes,)

# we want the command to be a list, but accomodate when given a string
cmd = command
if type(cmd) == type('string'):
cmd = shlex.split(command)

proc = subprocess.Popen(cmd,
stdin = stdin,
stdout = subprocess.PIPE,
stderr = subprocess.PIPE)

out, err = proc.communicate()

if proc.returncode not in expected_retcodes:
# when nothing gets to stderr, add stdout to Detail
if err.strip() == '':
err = out

mesg = 'Error [%d]: %s' % (proc.returncode, command)
mesg += '\nDetail: %s' % err
raise Exception, mesg

return proc.returncode, out, err

Regards,
--
dim