[GRASS-dev] Python Scripting Library: mogrify command

GRASS GIS GRASS GIS developer
1

Hi,
I was wandering: does exist a python::core function capable to mogrigy the inputs of a run_command()?

The mogrify function for psycopg2 is defined as follows:
“Return a query string after arguments binding. The string returned is exactly the one that would be sent to the database running the execute() method or similar.”

cur.mogrify(“INSERT INTO test (num, data) VALUES (%s, %s)”, (42, ‘bar’))
“INSERT INTO test (num, data) VALUES (42, E’bar’)”

…so for GRASS it could be:

grass.mogrify_command(“r.univar”,flags=“g”,map=“test”)
“r.univar -g map=test”

This could be helpful in debugging…

Maxi

··· 
-- 

Dr. Eng. Massimiliano Cannata
Responsabile Area Geomatica
Istituto Scienze della Terra
Scuola Universitaria Professionale della Svizzera Italiana
Via Trevano, c.p. 72
CH-6952 Canobbio-Lugano
Tel: +41 (0)58 666 62 14
Fax +41 (0)58 666 62 09
2

Massimiliano Cannata wrote:

I was wandering: does exist a python::core function capable to mogrigy
the inputs of a run_command()?

The mogrify function for psycopg2 is defined as follows:
"/Return a query string after arguments binding. The string returned is
exactly the one that would be sent to the database running the execute()
method or similar./"
>>> cur.mogrify("INSERT INTO test (num, data) VALUES (%s, %s)", (42,
'bar'))
"INSERT INTO test (num, data) VALUES (42, E'bar')"

...so for GRASS it could be:
>>> grass.mogrify_command("r.univar",flags="g",map="test")
"r.univar -g map=test"

make_command() returns an argument list, e.g.:

  > import grass.script as grass
  > grass.make_command("r.univar",flags="g",map="test")
  ['r.univar', '-g', 'map=test']

This is what all of the *_command() functions use to generate the
argument list.

Converting an argument list to a string is non-portable (/bin/sh has
significantly different syntax to cmd.exe) and quite tricky unless
you're willing to blindly quote everything to be on the safe side,
e.g. (for /bin/sh):

  args = [arg.replace("'", "'\\''") for arg in args]
  cmdstr = "'" + "' '".join(args) + "'"

It's much harder for Windows; see:

  http://msdn.microsoft.com/en-us/library/17w5ykft.aspx

or escape_arg() in lib/gis/spawn.c, or list2cmdline() in Python's
subprocess.py.

Note that none of the *_command() functions construct a command
string; they pass the argument list to subprocess.Popen() which
eventually either passes it to execve() (on Unix) or uses
list2cmdline() (on Windows).

--
Glynn Clements <glynn@gclements.plus.com>

3

Thanks Glynn for clarification,
I will go with the make_command()...

Maxi

On 07/13/2011 11:26 AM, Glynn Clements wrote:

Massimiliano Cannata wrote:

I was wandering: does exist a python::core function capable to mogrigy
the inputs of a run_command()?

The mogrify function for psycopg2 is defined as follows:
"/Return a query string after arguments binding. The string returned is
exactly the one that would be sent to the database running the execute()
method or similar./"
  >>> cur.mogrify("INSERT INTO test (num, data) VALUES (%s, %s)", (42,
'bar'))
"INSERT INTO test (num, data) VALUES (42, E'bar')"

...so for GRASS it could be:
  >>> grass.mogrify_command("r.univar",flags="g",map="test")
"r.univar -g map=test"

make_command() returns an argument list, e.g.:

  > import grass.script as grass
  > grass.make_command("r.univar",flags="g",map="test")
  ['r.univar', '-g', 'map=test']

This is what all of the *_command() functions use to generate the
argument list.

Converting an argument list to a string is non-portable (/bin/sh has
significantly different syntax to cmd.exe) and quite tricky unless
you're willing to blindly quote everything to be on the safe side,
e.g. (for /bin/sh):

  args = [arg.replace("'", "'\\''") for arg in args]
  cmdstr = "'" + "' '".join(args) + "'"

It's much harder for Windows; see:

  http://msdn.microsoft.com/en-us/library/17w5ykft.aspx

or escape_arg() in lib/gis/spawn.c, or list2cmdline() in Python's
subprocess.py.

Note that none of the *_command() functions construct a command
string; they pass the argument list to subprocess.Popen() which
eventually either passes it to execve() (on Unix) or uses
list2cmdline() (on Windows).

--

Dr. Eng. Massimiliano Cannata
Responsabile Area Geomatica
Istituto Scienze della Terra
Scuola Universitaria Professionale della Svizzera Italiana
Via Trevano, c.p. 72
CH-6952 Canobbio-Lugano
Tel: +41 (0)58 666 62 14
Fax +41 (0)58 666 62 09