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Command-line app helper library

Project description

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Arseparse is a simple Python utility/micro framework for writing command line interfaces. It provides some functionality around argparse that covers some common scenarios.


pip install arseparse

Basic usage:

from arseparse import Parser, Option

parser = Parser()

# register a command that returns the square of an int
parser.register('square', lambda value: value**2, [Option('value', type=int)])

# register a command that simply returns a string
parser.register('ping', lambda: 'pong')

# or with a decorator
@parser.register_dec([Option('value', type=int)])
def cube(value):
    return value**3


You can then point an application entrypoint to the script or execute the file: square 2

So far so boring. A more common scenario is to have a config file as the first argument, parse it, create objects that the command depends on, and pass those alongside the parsed attributes. The root_options and bootstrap constructor args to Parser allow us to implement this:

from arseparse import Parser, Option
import myapp

# these are options that come before our main command
root_options = [Option('config', type=str, help='path to ini file')]

# this lets us process/modify the kwargs before we execute the callable.
# we can rely on attributes resulting from root_options to be set.
# here config gets replaced by three objects: settings, db_session and user_svc
def bootstrap(**kwargs):
    config_uri = kwargs.pop('config')
    settings = myapp.parse_app_config(config_uri)
    dbsession = myapp.get_sessionmaker(settings)()
    user_svc = myapp.UserService(dbsession)
    kwargs.update(dict(settings=settings, dbsession=dbsession, user_svc=user_svc))
    return kwargs

parser = Parser(root_options, bootstrap)

@parser.register_dec([Option('username', type=str), Option('secret', type=str)])
def create_user(username, secret, user_svc, **kwargs):
    user_svc.create_user(username, secret)

@parser.register_dec([Option('user_id', type=int)])
def ban_user(user_id, user_svc, **kwargs):

def print_settings(settings, **kwargs):

You can now provide the path to a config file as the first argument: config.ini ban_user 23

Another common requirement is to be able to jump into a shell where some objects have been preconfigured for us. Here’s a simple recipe for that:

def shell(**kwargs):
    import IPython

Calling config.ini shell will drop you in an ipython shell where dbsession, settings and user_svc are in scope.

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