Merge pull request #9 from styleseat/master

Fix ZeroDivisionError in harmonic_mean
avalente · Jun 17, 2016 · 366fc7e · 366fc7e
2 parents 36740c9 + b469638
commit 366fc7e
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diff --git a/appmetrics/statistics.py b/appmetrics/statistics.py
@@ -399,7 +399,8 @@ def harmonic_mean(data):
     if not data:
         raise StatisticsError('harmonic_mean requires at least one data point')
 
-    return len(data) / sum(map(lambda x: 1.0 / x if x else 0.0, data))
+    divisor = sum(map(lambda x: 1.0 / x if x else 0.0, data))
+    return len(data) / divisor if divisor else 0.0
 
 
 def skewness(data):

diff --git a/appmetrics/tests/test_statistics.py b/appmetrics/tests/test_statistics.py
@@ -216,6 +216,9 @@ def test_harmonic_mean():
         fun = lambda data, expected: nt.assert_almost_equal(mm.harmonic_mean(data), expected)
         yield fun, data, expected
 
+def test_harmonic_mean_zero_divisor():
+    assert mm.harmonic_mean([0.0]) == 0.0
+
 @nt.raises(StatisticsError)
 def test_harmonic_mean_empty():
     mm.harmonic_mean([])