Fix empty bar graphs

pygal/bar.py

@@ -58,15 +58,16 @@ class Bar(Graph):
         return map(str, self.get_data_values())
 
     def data_max(self):
-        return max(chain(*map(lambda set: set['data'], self.data)))
+        return max(
+            list(chain(*map(lambda set: set['data'], self.data))) + [0])
         # above is same as
         # return max(map(lambda set: max(set['data']), self.data))
 
     def data_min(self):
         if not getattr(self, 'min_scale_value') is None:
             return self.min_scale_value
-        min_value = min(chain(*map(lambda set: set['data'], self.data)))
-        min_value = min(min_value, 0)
+        min_value = min(list(
+            chain(*map(lambda set: set['data'], self.data))) + [0])
         return min_value
 
     def get_bar_gap(self, field_size):
@@ -103,8 +104,12 @@ class VerticalBar(Bar):
         min_value = self.data_min()
         unit_size = (
             float(self.graph_height) - self.font_size * 2 * self.top_font)
-        unit_size /= (
+        divisor = (
             max(self.get_data_values()) - min(self.get_data_values()))
+        if divisor == 0:
+            unit_size = 0
+        else:
+            unit_size /= divisor
 
         bar_gap = self.get_bar_gap(self.get_field_width())
 

pygal/css/graph.css

@@ -4,7 +4,7 @@
   font-family: helvetica;
 }
 .svgBackground{
-  fill: transparent;
+  fill: #fff;
 }
 .graphBackground{
   fill: #e8eef6;
@@ -153,11 +153,11 @@
 }
 
 .light2 {
-  stop-color: #38588e;
+  stop-color: #476fb2;
 }
 
 .light3 {
-  stop-color: #476fb2;
+  stop-color: #38588e;
 }
 
 .light4 {

pygal/graph.py

@@ -292,14 +292,19 @@ class Graph(object):
         return 0
 
     def get_field_width(self):
-        return (float(
-            self.graph_width - self.font_size * 2 * self.right_font) /
-                (len(self.get_x_labels()) - self.right_align))
+        divisor = (len(self.get_x_labels()) - self.right_align)
+        if divisor == 0:
+            return 0
+        return float(
+            self.graph_width - self.font_size * 2 * self.right_font) / divisor
     field_width = get_field_width
 
     def get_field_height(self):
-        return (float(self.graph_height - self.font_size * 2 * self.top_font) /
-                (len(self.get_y_labels()) - self.top_align))
+        divisor = (len(self.get_y_labels()) - self.top_align)
+        if divisor == 0:
+            return 0
+        return float(
+            self.graph_height - self.font_size * 2 * self.top_font) / divisor
     field_height = get_field_height
 
     def draw_y_labels(self):

pygal/util/boundary.py

@@ -52,7 +52,7 @@ def calculate_bottom_margin(graph):
         max_x_label_height_px = graph.x_label_font_size
         if graph.x_label_rotation:
             label_lengths = map(len, graph.get_x_labels())
-            max_x_label_len = reduce(max, label_lengths)
+            max_x_label_len = reduce(max, label_lengths, 0)
             max_x_label_height_px *= max_x_label_len * 0.6
             max_x_label_height_px *= sin(graph.x_label_rotation)
         bb += max_x_label_height_px + graph.y_label_font_size
@@ -85,7 +85,8 @@ def calculate_left_margin(graph):
         bl += graph.y_title_font_size + 5
     if graph.x_label_rotation:
         first_x_label_width = (
-            graph.x_label_font_size * len(graph.get_x_labels()[0]) * 0.6)
+            graph.x_label_font_size * len(
+                (graph.get_x_labels() or [[0]])[0]) * 0.6)
         bl = max(bl, first_x_label_width * cos(graph.x_label_rotation))
     return bl