add std() test case

TimeSeries.py

@@ -272,6 +272,11 @@ def mean(self):
         -------
         float
             the mean of self.values
+
+        Raises
+        ------
+        ValueError
+            If self.values is empty
         """
         if(len(self._values) == 0):
             raise ValueError("cant calculate mean of length 0 list")
@@ -294,6 +299,24 @@ def median(self):
         if(len(self._values) == 0):
             raise ValueError("cant calculate median of length 0 list")
         return np.median(self._values)
+
+    def std(self):
+        '''
+        Returns the standard-deviation of self.values
+
+        Returns
+        -------
+        float
+            the standard deviation of self.values
+
+        Raises
+        ------
+        ValueError
+            If self.values is empty
+        '''
+        if(len(self._values) == 0):
+            raise ValueError("cant calculate median of length 0 list")
+        return np.std(self._values)
 
     def interpolate(self, times):
         '''

test_TimeSeries.py

@@ -39,12 +39,19 @@ def test_median_empty():
     with raises(ValueError):
          TS.TimeSeries([],[]).median()
 
+def test_std_empty():
+    with raises(ValueError):
+        TS.TimeSeries([],[]).std()
+
 def test_mean():
     assert testSeries.mean() == 2.5
 
 def test_median():
     assert testSeries.median() == 2.5
 
+def test_std():
+    assert testSeries.std() == 1.1180339887498949
+
 def test_itertimes():
     ti=testSeries.itertimes()
     assert next(ti)==0