wat.py

class Foo(object):
	def __init__(s, foo):
		s.wrapped = foo

	def __getattr__(s, attr):
		target = attr
		if attr.startswith('__') and not attr.endswith('__'):
			target = '_{}{}'.format(s.wrapped.__class__.__name__, attr)
		return getattr(s.wrapped, target)


class Other(object):
	def __spec(s):
		print(123)
	def __len__(s):
		return 5

inner = Other()
a = Foo(inner)

print(dir(a))
print(dir(inner))
print(a.__len__())
print(len(a))  # Wat