Gutter for AppEngine

gutter-appengine provides an App Engine front-end for gutter. It allows you to create and update switches using a UI and to register new arguments and operators particular to your application.

Getting Started

The first step is to include gutter-appengine in your app.yaml.

includes:
- lib/gutter/appengine/

Next, in appengine_config.py set the default gutter manager to use the App Engine manager.

from gutter.client.settings import manager
from gutter.appengine.manager import default_manager

manager.default = default_manager

Now, you are ready to define your switches and switch conditions. Also in appengine_config.py (and above setting the default manager so that the manager knows how to unpickle the classes).

from gutter.client import arguments
from gutter.appengine import registry


class User(arguments.Container):

    nickname = arguments.String(lambda self: self.input.nickname())
    email = arguments.String(lambda self: self.input.email())
    user_id = arguments.String(lambda self: self.input.user_id())


class Account(arguments.Container):

    account_group_id = arguments.String(lambda self: self.input.account_group_id())


class Partner(arguments.Container):

    partner_id = arguments.String(lambda self: self.input.partner_id)


registry.arguments.register(User.email)
registry.arguments.register(User.nickname)
registry.arguments.register(User.user_id)
registry.arguments.register(Account.account_group_id)

Navigate to /gutter/ to begin creating switches. The example in example_app shows a full example of integrating gutter with your project.

Defining Switches

A Switch takes one or more Conditions and passes or fails based on whether or not its input satisfies the Conditions. Each Condition takes one or more Arguments. You can think of this as defining a list of equations that any inputs must satisfy to pass or fail a switch.

class UserArguments(arguments.Container):
    age = arguments.Integer(lambda self: self.input.age())

condition = Condition(UserArguments, 'age', LessThan(upper_limit=18))

switch = Switch('minor', compounded=False)
switch.conditions = [condition]

Using Switches

To use a switch, call active and pass it an input. The input can be any object matching the Arguments to your Condition. active will return True if the input satisfies the condition or False otherwise.

from gutter.client.default import gutter

is_active = gutter.active('minor', User)  # User is your domain object

More Information

If you need more information on gutter internals, refer to the official gutter project.

Development

Using virtualenv is recommended for development.

virtualenv .
source ./bin/activate
Development Dependencies

We use flake8 for checking both PEP-8 and common Python errors and invoke for continuous integration.

pip install -U flake8
pip install -U invoke

You can list available build tasks with inv -l.

Due to a limitation with Google Appengine, dependencies must be installed locally before running tests. TThe fetch_deps make command will install dependencies to the vendor directory.

inv fetch_deps

Publishing to PyPI

You need pip, setuptools and wheel to publish to PyPI.

inv publish