Re: python + postgres psql + os.popen
hi, there. thanks for the help.
now i have a different problem now. i decided to use 'subprocess' and
'Popen' objects instead of 'os.popen()' function, which i believe do
not make much difference.
my code is like the following...
[1] link = subprocess.Popen(command, stdin = subprocess.PIPE, stdout =
subprocess.PIPE, stderr = subprocess.PIPE, shell = True)
[2] link.communicate(password)
[3] link.wait()
[4] err = link.communicate()[1]
[5] if err != None: print str(err)
i have read several threads about 'subprocess' posted on this group and
still i have way too much confusion regarding the above section of
code.
1. i'm currently using MS Windows.
i remember some have said that communicate() function is not usable on
this OS.
could anyone confirm this?
2. i'm expecting an error message, as i am trying to create a table
which does already exist in the database.
but if i try to print out the error message as [5], it is just an EMPTY
string.
and, if i try the SAME THING using command-line, i get a correct error
message this time ('psql:createstudent.sql:12: ERROR: relation
student already exists').
HOWEVER, if i comment out [2] link.communicate(password), meaning i do
not supply a password, it shows an error message, 'psql: fe_sendauth:
no password supplied', which is correct as expected.
my question is...
why does it work (i.e. showing a correct error message) when no
password supplied but NOT when creating a table which already exists in
the database? it should work for both cases.
thank you very much.
Simon Forman wrote:
damacy wrote:
hello, everyone.
...
this works well. however, it does not show me any warning nor error
messages if there is one. for example, i am trying to create a table
which already exists in the database, it should show me a warning/error
message saying there already is one present in the database, or
something like that.
can anyone help me?
I recently needed to use psql from python on a computer that I couldn't
install psycopg on and I used something similar to this to do it (I
edited the code slightly to make it clearer):
from subprocess import Popen, PIPE
# Pass the password through an environment
# variable to prevent psql asking for it.
psql_env = dict(PGPASSWORD='')
# Create the subprocess.
proc = Popen(cmd, shell=True, env=psql_env, stdout=PIPE, stderr=PIPE)
# Try reading it's data.
data = proc.stdout.read()
# Check for errors.
err = proc.stderr.read()
if err: raise Exception(err)
It worked nicely for me, YMMV.
Hope that helps,
~Simon
--
http://mail.python.org/mailman/listinfo/python-list
Re: python + postgres psql + os.popen
hi, there. thanks for the help.
now i have a different problem now. i decided to use 'subprocess' and
'Popen' objects instead of 'os.popen()' function, which i believe do
not make much difference.
my code is like the following...
[1] link = subprocess.Popen(command, stdin = subprocess.PIPE, stdout =
subprocess.PIPE, stderr = subprocess.PIPE, shell = True)
[2] link.communicate(password)
[3] link.wait()
[4] err = link.communicate()[1]
[5] if err != None: print str(err)
i have read several threads about 'subprocess' posted on this group and
still i have way too much confusion regarding the above section of
code.
1. i'm currently using MS Windows.
i remember some have said that communicate() function is not usable on
this OS.
could anyone confirm this?
2. i'm expecting an error message, as i am trying to create a table
which does already exist in the database.
but if i try to print out the error message as [5], it is just an EMPTY
string.
and, if i try the SAME THING using command-line, i get a correct error
message this time ('psql:createstudent.sql:12: ERROR: relation
student already exists').
HOWEVER, if i comment out [2] link.communicate(password), meaning i do
not supply a password, it shows an error message, 'psql: fe_sendauth:
no password supplied', which is correct as expected.
my question is...
why does it work (i.e. showing a correct error message) when no
password supplied but NOT when creating a table which already exists in
the database? it should work for both cases.
thank you very much.
Simon Forman wrote:
damacy wrote:
hello, everyone.
...
this works well. however, it does not show me any warning nor error
messages if there is one. for example, i am trying to create a table
which already exists in the database, it should show me a warning/error
message saying there already is one present in the database, or
something like that.
can anyone help me?
I recently needed to use psql from python on a computer that I couldn't
install psycopg on and I used something similar to this to do it (I
edited the code slightly to make it clearer):
from subprocess import Popen, PIPE
# Pass the password through an environment
# variable to prevent psql asking for it.
psql_env = dict(PGPASSWORD='')
# Create the subprocess.
proc = Popen(cmd, shell=True, env=psql_env, stdout=PIPE, stderr=PIPE)
# Try reading it's data.
data = proc.stdout.read()
# Check for errors.
err = proc.stderr.read()
if err: raise Exception(err)
It worked nicely for me, YMMV.
Hope that helps,
~Simon
--
http://mail.python.org/mailman/listinfo/python-list
Re: python + postgres psql + os.popen
damacy írta: hello, everyone. i am trying to write a program which executes SQL commands stored in .sql files. i wrote a function called psql() whose contents look like the following. ... os.popen(command) file = os.popen(command, 'w') file.write(password) file.close() ... where command looks like psql -h [host] -d [dbname] -U [username] -W -f [filename] this works well. however, it does not show me any warning nor error messages if there is one. for example, i am trying to create a table which already exists in the database, it should show me a warning/error message saying there already is one present in the database, or something like that. can anyone help me? You can put this in the beginning of your SQL file: \set ON_ERROR_STOP If you also want to know what command caused the error: \set ECHO all You can also use a library written for Python. For example, psycopg http://initd.org/projects/psycopg1 Best, Laszlo -- http://mail.python.org/mailman/listinfo/python-list
Re: python + postgres psql + os.popen
damacy wrote:
hello, everyone.
i am trying to write a program which executes SQL commands stored in
.sql files.
i wrote a function called psql() whose contents look like the
following.
...
os.popen(command)
file = os.popen(command, 'w')
file.write(password)
file.close()
...
where command looks like
psql -h [host] -d [dbname] -U [username] -W -f [filename]
this works well.
But is a very strange way to access a RDBMS from Python code. Are you
aware of the existence of db modules ?
can anyone help me?
http://www.python.org/dev/peps/pep-0249/
http://initd.org/projects/psycopg1
--
bruno desthuilliers
python -c print '@'.join(['.'.join([w[::-1] for w in p.split('.')]) for
p in '[EMAIL PROTECTED]'.split('@')])
--
http://mail.python.org/mailman/listinfo/python-list
Re: python + postgres psql + os.popen
damacy wrote: hello, everyone. ... this works well. however, it does not show me any warning nor error messages if there is one. for example, i am trying to create a table which already exists in the database, it should show me a warning/error message saying there already is one present in the database, or something like that. can anyone help me? I recently needed to use psql from python on a computer that I couldn't install psycopg on and I used something similar to this to do it (I edited the code slightly to make it clearer): from subprocess import Popen, PIPE # Pass the password through an environment # variable to prevent psql asking for it. psql_env = dict(PGPASSWORD='') # Create the subprocess. proc = Popen(cmd, shell=True, env=psql_env, stdout=PIPE, stderr=PIPE) # Try reading it's data. data = proc.stdout.read() # Check for errors. err = proc.stderr.read() if err: raise Exception(err) It worked nicely for me, YMMV. Hope that helps, ~Simon -- http://mail.python.org/mailman/listinfo/python-list
python + postgres psql + os.popen
hello, everyone. i am trying to write a program which executes SQL commands stored in .sql files. i wrote a function called psql() whose contents look like the following. ... os.popen(command) file = os.popen(command, 'w') file.write(password) file.close() ... where command looks like psql -h [host] -d [dbname] -U [username] -W -f [filename] this works well. however, it does not show me any warning nor error messages if there is one. for example, i am trying to create a table which already exists in the database, it should show me a warning/error message saying there already is one present in the database, or something like that. can anyone help me? -- http://mail.python.org/mailman/listinfo/python-list
