It is often useful to have command line scripts that can access the model of a TurboGears2 application, as an example, to manipulate model object from within a cron job. The main difficulty in implementing such a script is often to have the model configured according to a given configuration file. Paste takes care of that but the documentation of it’s API can seem somewhat obscure to newcomers.
The following script prints all the usernames to the console. The critical part of the script is the load_config() function. It both parses the .ini configuration file and initializes the SQLAlchemy model.
#!/usr/bin/env python
""" Print all the usernames to the console. """
import os
import sys
from argparse import ArgumentParser
from paste.deploy import appconfig
from example_app.config.environment import load_environment
from example_app import model
def load_config(filename):
conf = appconfig('config:' + os.path.abspath(filename))
load_environment(conf.global_conf, conf.local_conf)
def parse_args():
parser = ArgumentParser(description=__doc__)
parser.add_argument("conf_file", help="configuration to use")
return parser.parse_args()
def main():
args = parse_args()
load_config(args.conf_file)
print model.DBSession.query(model.User.user_name).all()
if __name__ == '__main__':
sys.exit(main())
Setuptools can take care of installing CLI script in the $PATH when
an application is installed or set it development mode. For this
to happen, all what one have to do is to include a reference to his
scripts in the console_scripts entry point in setup.py. As an
example, if the above script is saved in saved as
exampleapp/scripts/usernames.py, then setup.py should contain the
following:
setup(#...
entry_points="""
# ...
[console_scripts]
print-usernames = exampleapp.scripts.usernames:main
""")
The TGExt.Command package provides a class which can be used to provide more involved command support, including support for respecting PID files, and integration with the paster command-line parsing code.