Return 0 for a single value tracker

.bumpversion.cfg

@@ -1,5 +1,5 @@
 [bumpversion]
-current_version = 0.3.1-dev3
+current_version = 0.3.3-dev0
 commit = True
 tag = False
 parse = (?P<major>\d+)\.(?P<minor>\d+)\.(?P<patch>\d+)(\-(?P<release>[a-z]+)(?P<build>\d+))?

docs/conf.py

@@ -119,7 +119,7 @@ def setup(app):
 # built documents.
 #
 # The short X.Y version.
-version = "0.3.1-dev3"
+version = "0.3.3-dev0"
 # The full version, including alpha/beta/rc tags.
 release = ""  # Is set by calling `setup.py docs`
 

setup.cfg

@@ -4,7 +4,7 @@
 
 [metadata]
 name = whylogs
-version = 0.3.1-dev3
+version = 0.3.3-dev0
 description = Profile and monitor your ML data pipeline end-to-end
 author = WhyLabs.ai
 author-email = support@whylabs.ai

src/whylogs/_version.py

@@ -1,3 +1,3 @@
 """WhyLabs version number."""
 
-__version__ = "0.3.1-dev3"
+__version__ = "0.3.3-dev0"

src/whylogs/core/statistics/datatypes/variancetracker.py

@@ -52,10 +52,11 @@ def variance(self):
         """
         Return an estimate of the sample variance
         """
-        try:
-            return self.sum / (self.count - 1)
-        except ZeroDivisionError:
+        if self.count == 0:
             return math.nan
+        if self.count == 1:
+            return 0
+        return self.sum / (self.count - 1)
 
     def merge(self, other: "VarianceTracker"):
         """

tests/unit/core/statistics/datatypes/test_variancetracker.py

@@ -5,6 +5,14 @@
 from whylogs.core.statistics.datatypes import VarianceTracker
 
 
+def test_single_value():
+    tracker = VarianceTracker()
+    tracker.update(1.0)
+
+    assert tracker.count == 1
+    assert tracker.variance() == 0
+
+
 def test_update():
     vals = [1.0, 2.0, 3]
     tracker = VarianceTracker()