Recursion depth exceeded

gistfile1.py

class Node:
	def __init__(self, b, e, data, L, R):
		self.b = b
		self.e = e

		self.L = L
		self.R = R

		self.data = data

class SegmentTree:
	def __init__(self, N, quads):
		def _init(b, e):
			if b is e:
				data = 'foo' #No dependency
				return Node(b, e, data, None, None)
			else:
				mid = (b + e ) / 2

				L = _init(b, mid)
				R = _init(mid + 1, e)

				data = 'foo' #Data depends on values in L and R

				return Node(b, e, q, L, R)

		self.root = _init(1, N)