Fix learn_rounding_scheme for more than 14 digits

rdt/transformers/numerical.py

@@ -80,13 +80,19 @@ def _learn_rounding_digits(data):
         # check if data has any decimals
         data = np.array(data)
         roundable_data = data[~(np.isinf(data) | pd.isna(data))]
-        if ((roundable_data % 1) != 0).any():
-            if (roundable_data == roundable_data.round(MAX_DECIMALS)).all():
-                for decimal in range(MAX_DECIMALS + 1):
-                    if (roundable_data == roundable_data.round(decimal)).all():
-                        return decimal
 
-        return None
+        # Doesn't contain decimal digits
+        if ((roundable_data % 1) == 0).all():
+            return None
+
+        # Try to round to fewer digits
+        if (roundable_data == roundable_data.round(MAX_DECIMALS)).all():
+            for decimal in range(MAX_DECIMALS + 1):
+                if (roundable_data == roundable_data.round(decimal)).all():
+                    return decimal
+
+        # Can't round, not equal after MAX_DECIMALS digits of precision
+        return MAX_DECIMALS
 
     def _raise_out_of_bounds_error(self, value, name, bound_type, min_bound, max_bound):
         raise ValueError(

tests/unit/transformers/test_numerical.py

@@ -32,13 +32,13 @@ def test__learn_rounding_digits_more_than_15_decimals(self):
         Input:
         - An array that contains floats with more than 15 decimals.
         Output:
-        - None
+        - 14
         """
         data = np.random.random(size=10).round(20)
 
         output = FloatFormatter._learn_rounding_digits(data)
 
-        assert output is None
+        assert output == 14
 
     def test__learn_rounding_digits_less_than_15_decimals(self):
         """Test the _learn_rounding_digits method with less than 15 decimals.
@@ -298,7 +298,7 @@ def test__fit_learn_rounding_scheme_true_max_decimals(self):
         Input:
         - Series with a value that has 15 decimals
         Side Effect:
-        - ``_rounding_digits`` is set to ``None``
+        - ``_rounding_digits`` is set to 14
         """
         # Setup
         data = pd.Series([0.000000000000001])
@@ -311,7 +311,7 @@ def test__fit_learn_rounding_scheme_true_max_decimals(self):
         transformer._fit(data)
 
         # Asserts
-        assert transformer._rounding_digits is None
+        assert transformer._rounding_digits == 14
 
     def test__fit_learn_rounding_scheme_true_inf(self):
         """Test ``_fit`` with ``learn_rounding_scheme`` set to ``True``.