PartialObject (as functools.partial is to functions)

partial_object.py

#!/usr/bin/env python2.7
# -*- coding: utf-8 -*-

from __future__ import division, absolute_import, print_function, unicode_literals

import inspect
from collections import OrderedDict


class PartialManager(type):
	def __call__(cls, *args, **kwargs):
		signature = inspect.getargspec(cls.__init__)
		arg_names = signature.args[1:]
		
		if signature.defaults:
			arg_names = arg_names[:-len(signature.defaults)]
		
		if (len(args) + sum(arg in kwargs for arg in arg_names)) >= len(arg_names):
			return super(PartialManager, cls).__call__(*args, **kwargs)
		
		else:
			return getattr(cls, '__partialclass__', PartialObject)(cls, *args, **kwargs)


class PartialObject(object):
	def __init__(self, cls, *args, **kwargs):
		self.cls = cls
		self.args = args
		self.kwargs = kwargs
		
		self.args, self.kwargs = self.modify(self.args, self.kwargs)
		
		signature = inspect.getargspec(self.cls.__init__)
		self.arg_names = signature.args[1:]
		
		if signature.defaults:
			self.arg_names = self.arg_names[:-len(signature.defaults)]
			self.default_kwargs = OrderedDict(zip(signature.args[-len(signature.defaults):], signature.defaults))
		
		else:
			self.default_kwargs = OrderedDict()
	
	def __call__(self, *args, **kwargs):
		new_args = self.args + args
		new_kwargs = self.kwargs.copy()
		new_kwargs.update(kwargs)
		
		new_args, new_kwargs = self.modify(new_args, new_kwargs)
		
		return self.cls(*new_args, **new_kwargs)
	
	def modify(self, args, kwargs):
		return (args, kwargs)
	
	def __unicode__(self):
		applied = list(self.arg_names)[:len(self.args)]
		kwargs = self.kwargs.copy()
		
		for arg_name in self.arg_names:
			if arg_name in kwargs:
				del(kwargs[arg_name])
				applied.append(arg_name)
		
		for kwarg, default in self.default_kwargs.iteritems():
			if kwarg in kwargs:
				if kwargs[kwarg] != default:
					applied.append(kwarg)
				
				del(kwargs[kwarg])
		
		applied.extend(kwargs.iterkeys())
		
		return 'Partial %s (Applied: %s)' % (self.cls.__name__, ', '.join(applied) if applied else None)
	
	def __str__(self):
		return unicode(self).encode('utf-8')
	
	def __repr__(self):
		args = self.args[:]
		kwargs = self.kwargs.copy()
		args += tuple((kwargs.pop(arg_name) for arg_name in self.arg_names if arg_name in kwargs))
		
		args = (
			['%s' % repr(arg) for arg in args] +
			['%s=%s' % (kwarg, repr(kwargs[kwarg])) for kwarg, default in self.default_kwargs.iteritems() if kwarg in kwargs and kwargs[kwarg] != default] +
			['%s=%s' % (kwarg, repr(value)) for kwarg, value in kwargs.iteritems() if kwarg not in self.default_kwargs]
		)
		
		return '%s(%s%s)' % (self.__class__.__name__, self.cls.__name__, ', %s' % ', '.join(args) if args else '')

usage.py

#!/usr/bin/env python2.7
# -*- coding: utf-8 -*-

from __future__ import division, absolute_import, print_function, unicode_literals

from partial_object import PartialManager, PartialObject


class PartialTest(PartialObject):
	def modify(self, args, kwargs):
		'''
		Allows supplying arguments out of order.
		
		'''
		
		if args and isinstance(args[0], int) and 'count' not in kwargs:
			args = list(args)
			kwargs['count'] = args.pop(0)
			args = tuple(args)
		
		return (args, kwargs)


class Test(object):
	__metaclass__ = PartialManager
	__partialclass__ = PartialTest
	
	def __init__(self, name, count):
		for i in xrange(count):
			print(name)