python-main-wrapper

Set up global environment and run another script within, ala pdb, profile, etc

Use main-wrapper either as a command-line script or as a library to make Python scripts that set up or change some global Python environment and then run another script within that environment. It seeks to combine into one library all the gloss and polish of other Python software that does this, such as using python -m with pdb and profile in the standard library or the coverage package's command-line run command.

Installation

Install using any tool for installing standard Python 3 distributions such as pip:

$ sudo pip3 install main-wrapper

Usage

You may use this package either as a library in your code that needs to wrap another script or as a command-line script.

To use as a library, use the provided decorator to wrap your function that sets up the global environment you need the script to be run in:

import logging
import argparse

import mainwrapper

parser = argparse.ArgumentParser()
parser.add_argument(
    "--level",
    default="INFO",
    help="The level of messages to log at or above",
)

@mainwrapper.wrap_main(parser)
def main(level=parser.get_default("level")):
    """
    As an example, this function will set up logging at level INFO.
    """
    logging.basicConfig(level=getattr(logging, level))

The changes to Python's global execution environment that support running the wrapper function and the final script are also cleaned up upon completion, so it should be possible to use this library to execute multiple scripts in the same process as if they were run independently.

See the command-line help for details the options and arguments for using this package as a command-line script:

$ usage: python-main-wrapper [-h] wrapper script

Set up global environment and run another script within, ala pdb, profile, etc..  Both
script arguments may either be a path to a Python script, a Python module or package
to be run in the same manner as Python's `-m` option, or a setuptools
`path.to.import:callable` entry-point.

positional arguments:
  wrapper     A Python script that sets up the environment
  script      The Python script to run within the wrapper's environment

optional arguments:
  -h, --help  show this help message and exit

Note that this package uses argparse.ArgumentParser.parse_known_args under the hood and as such be sure to use it's support for the -- convention to separate arguments and options to be passed to the wrapped script:

$ python-main-wrapper site site:_script --help
...
site.py [--user-base] [--user-site]

Without arguments print some useful information
With arguments print the value of USER_BASE and/or USER_SITE separated
by ':'.

Exit codes with --user-base or --user-site:
  0 - user site directory is enabled
  1 - user site directory is disabled by user
  2 - user site directory is disabled by super user
      or for security reasons
 >2 - unknown error

Motivation

I found myself writing such wrapper scripts repeatedly over the years and kept struggling to remember how I did it last time. I made this package to capture all that knowledge and to have one place to put improvements as I discover them.