#937: Add check for pandas null in json conversion. (#938)

* #937: Add check for pandas null in json conversion.

* #937: Check that object isn't sequence before checking for null.

src/evidently/utils/numpy_encoder.py

@@ -1,5 +1,6 @@
 import datetime
 import json
+import typing
 import uuid
 from typing import Callable
 from typing import Tuple
@@ -47,8 +48,14 @@ def default(self, o):
 
         If we cannot convert the object, leave the default `JSONEncoder` behaviour - raise a TypeError exception.
         """
+
+        # check mapping rules
         for types_list, python_type in _TYPES_MAPPING:
             if isinstance(o, types_list):
                 return python_type(o)
 
+        # explicit check pandas null
+        if not isinstance(o, typing.Sequence) and pd.isnull(o):
+            return None
+
         return json.JSONEncoder.default(self, o)

src/evidently/utils/visualizations.py

@@ -698,9 +698,13 @@ def make_hist_for_cat_plot(curr: pd.Series, ref: pd.Series = None, normalize: bo
 
 def get_distribution_for_category_column(column: pd.Series, normalize: bool = False) -> Distribution:
     value_counts = column.value_counts(normalize=normalize, dropna=False)
+
+    # filter out na values if it amount == 0
+    new_values = [(k, v) for k, v in value_counts.items() if (not pd.isna(k) or v > 0)]
+
     return Distribution(
-        x=value_counts.index.values,
-        y=value_counts.values,
+        x=[x[0] for x in new_values],
+        y=[x[1] for x in new_values],
     )