[ENH] Datadesc repr (#352)

* add a repr to DataDesc

* remove todo, fix docstring, move away from assertionerror

Author: zbarry

janitor/functions.py

@@ -2764,8 +2764,6 @@ class DataDescription:
     High-level description of data present in this DataFrame.
 
     This is a custom data accessor.
-
-    TODO: add repr, fail on type error in desc
     """
 
     def __init__(self, data):
@@ -2790,9 +2788,13 @@ def df(self) -> pd.DataFrame:
         """Get a table of descriptive information in a DataFrame format."""
         return self._get_data_df()
 
+    def __repr__(self):
+        """Human-readable representation of the `DataDescription` object."""
+        return str(self._get_data_df())
+
     def display(self):
         """Print the table of descriptive information about this DataFrame."""
-        print(self._get_data_df())
+        print(self)
 
     def set_description(self, desc: Union[List, Dict]):
         """
@@ -2801,7 +2803,13 @@ def set_description(self, desc: Union[List, Dict]):
         :param desc: The structure containing the descriptions to update
         """
         if isinstance(desc, list):
-            assert len(desc) == len(self._data.columns)
+            if len(desc) != len(self._data.columns):
+                raise ValueError(
+                    f"Length of description list "
+                    f"({len(desc)}) does not match number of columns in "
+                    f"DataFrame ({len(self._data.columns)})"
+                )
+
             self._desc = dict(zip(self._data.columns, desc))
 
         elif isinstance(desc, dict):

tests/functions/test_data_description.py

@@ -21,10 +21,10 @@ def test_description_list(dataframe):
 
     assert (df["description"] == desc).all()
 
-    with pytest.raises(AssertionError):
+    with pytest.raises(ValueError):
         dataframe.data_description.set_description([])
 
-    with pytest.raises(AssertionError):
+    with pytest.raises(ValueError):
         dataframe.data_description.set_description(desc[0:3])