Filtering now computes coverage percentages properly.

1 files changed, 9 insertions, 2 deletions

diff --git a/coverage/results.py b/coverage/results.py
index 6c41a94..5eff0f3 100644
--- a/coverage/results.py
+++ b/coverage/results.py
@@ -204,8 +204,8 @@ class Numbers(object):
     def pc_covered(self):
         """Returns a single percentage value for coverage."""
         if self.n_statements > 0:
-            pc_cov = (100.0 * (self.n_executed + self.n_executed_branches) /
-                        (self.n_statements + self.n_branches))
+            numerator, denominator = self.ratio_covered
+            pc_cov = (100.0 * numerator) / denominator
         else:
             pc_cov = 100.0
         return pc_cov
@@ -236,6 +236,13 @@ class Numbers(object):
             width += 1 + cls._precision
         return width
 
+    @property
+    def ratio_covered(self):
+        """Return a numerator and denominator for the coverage ratio."""
+        numerator = self.n_executed + self.n_executed_branches
+        denominator = self.n_statements + self.n_branches
+        return numerator, denominator
+
     def __add__(self, other):
         nums = Numbers()
         nums.n_files = self.n_files + other.n_files