first iteration of __isub__ method in RankingStat

gstlal-inspiral/python/stats/horizonhistory.py

@@ -254,6 +254,14 @@ class NearestLeafTree(object):
 			self[x] = val
 		return self
 
+	def __isub__(self, other):
+		for key, val in other.items():
+			if key in self:
+				del self[key]
+			else:
+				raise KeyError("NearestLeafTree object does not have an entry to subtract")
+		return self
+
 	def keys(self):
 		return [x for x, val in self.tree]
 
@@ -442,6 +450,14 @@ class HorizonHistories(dict):
 				self[key] = copy.deepcopy(history)
 		return self
 
+	def __isub__(self, other):
+		for key, history in other.items():
+			if key in self:
+				self[key] -= history
+			else:
+				raise KeyError("HorizonHistory object does not have a history key-ed by %s." % key)
+		return self
+
 	def minkey(self):
 		"""
 		Return the minimum key stored in the trees.