Fixed failing test case in Pie.add_data. Tests now pass on Python 3

svg/charts/pie.py

@@ -1,5 +1,5 @@
 import math
-from operator import add
+import itertools
 from lxml import etree
 from svg.charts.graph import Graph
 
@@ -90,9 +90,25 @@ class Pie(Graph):
 
 		is the same as:
 
-		graph.add_data({data:[3,5,8,11]}) # doctest: +SKIP
+		>>> graph.add_data({data:[3,5,8,11]}) # doctest: +SKIP
+
+		If data is added of with differing lengths, the corresponding
+		values will be assumed to be zero.
+
+		>>> graph.add_data({data:[1,2,3,4]}) # doctest: +SKIP
+		>>> graph.add_data({data:[5,7]}) # doctest: +SKIP
+
+		is the same as:
+
+		>>> graph.add_data({data:[5,7]}) # doctest: +SKIP
+		>>> graph.add_data({data:[1,2,3,4]}) # doctest: +SKIP
+
+		and
+
+		>>> graph.add_data({data:[6,9,3,4]}) # doctest: +SKIP
 		"""
-		self.data = map(robust_add, self.data, data_descriptor['data'])
+		pairs = itertools.izip_longest(self.data, data_descriptor['data'])
+		self.data = list(itertools.starmap(robust_add, pairs))
 
 	def add_defs(self, defs):
 		"Add svg definitions"
@@ -123,7 +139,7 @@ class Pie(Graph):
 		return ['']
 
 	def keys(self):
-		total = reduce(add, self.data)
+		total = sum(self.data)
 		percent_scale = 100.0 / total
 		def key(field, value):
 			result = [field]
@@ -157,7 +173,7 @@ class Pie(Graph):
 		wedge_text_pad = 5
 		wedge_text_pad = 20 * int(self.show_percent) * int(self.show_data_labels)
 
-		total = reduce(add, self.data)
+		total = sum(self.data)
 		max_value = max(self.data)
 
 		percent_scale = 100.0 / total