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Description:

progeny 0.2.0

Simple (but powerful) management for complex class hierarchies.

Motivation
While XYZClass.__subclasses__() returns the children of a class, there is
no built-in way to return all descendants. This is the core of Progeny’s
purpose.
In addition, Progeny provides tools to help manage complex, deeply nested
class hierarchies - hiding individual classes, keeping a registry of
descendants, etc.

Examples

Basic Usage
import progeny

class NotificationHandler(progeny.Base):
def send_message(self, *args, **kwargs):
raise RuntimeError

class CustomerOneNotificationHandler(NotificationHandler):
def send_message(self, *args, **kwargs):
# .. business logic ...

class CustomerTwoNotificationHandler(NotificationHandler):
def send_message(self, *args, **kwargs):
# .. business logic ...
Now we can iterate over all of the subclasses of NotificationHandler:
def send_newsletter():
for handler in NotificationHandler.progeny.values():
handler.send_message('Your attention, please!')

Omitting descendant classes
In some cases, it may be useful to prevent descendant classes from being visible to Progeny.
from progeny import progeny.Base

class NotificationHandler(progeny.Base):
def send_message(self, *args, **kwargs):
raise RuntimeError

class EmailNotificationHandler(NotificationHandler):
__progeny_tracked__ = False

def send_message(self, *args, **kwargs):
# .. business logic ..

class SmsNotificationHandler(NotificationHandler):
__progeny_tracked__ = False

def send_message(self, *args, **kwargs):
# .. business logic ..

class CustomerOneNotificationHandler(EmailNotificationHandler):
pass

class CustomerTwoNotificationHandler(SmsNotificationHandler):
pass
Any classes with __progeny_tracked__ set to a falsy value during class
construction will be ignored by Progeny. It’s descendant classes are unaffected:
NotificationHandler.progeny.values()
# {CustomerOneNotificationHandler, CustomerTwoNotificationHandler}
This can be especially handy to conditionally track subclasses based on config
context:
class CustomerFooNotificationHandler(EmailNotificationHandler):
__progeny_tracked__ = config.get('CUSTOMER_FOO_ACTIVE')

Using the descendants registry
Progeny makes it easy to choose between descendant classes at runtime:
from progeny import progeny.Base
from my_app.users import UserLevel

class UploadParser(progeny.Base):
pass

class FreeUserUploadParser(UploadParser):
__progeny_key__ = UserLevel.FREE

def parse_upload(self, *args, **kwargs):
# .. logic to parse the upload slowly, using shared resources

class PremiumUserUploadParser(UploadParser):
__progeny_key__ = UserLevel.PAID

def parse_upload(self, *args, **kwargs):
# .. logic to parse the upload immediately with dedicated resources
def parse_upload(data):
UploadParser.progeny.get(session.user.level).parse_upload(data)

Publishing to PyPI
python setup.py sdist bdist_wheel
twine upload "dist/*"