[ENH] Updated convert_excel_date to throw meaningful error

CHANGELOG.md

@@ -14,6 +14,7 @@
     to provide a simpler selection without the need for lists. - @samukweku
 -   [ENH] `encode_categoricals` refactored to use generic functions
     via `functools.dispatch`. - @samukweku
+-   [ENH] Updated convert_excel_date to throw meaningful error when values contain non-numeric. @nvamsikrishna05
 
 ## [v0.20.14] - 2021-03-25
 

examples/notebooks/inflating_converting_currency.ipynb

@@ -130,7 +130,7 @@
     "    lambda x: x.inflate_currency(\n",
     "        column_name='expenditure',\n",
     "        country='USA',\n",
-    "        currency_year=x.name,\n",
+    "        currency_year=int(x.name),\n",
     "        to_year=2018,\n",
     "        make_new_column=True\n",
     "    )\n",
@@ -271,4 +271,4 @@
  },
  "nbformat": 4,
  "nbformat_minor": 4
-}
+}

janitor/functions.py

@@ -24,6 +24,7 @@
 
 import numpy as np
 import pandas as pd
+from pandas.api.types import is_numeric_dtype
 import pandas_flavor as pf
 from multipledispatch import dispatch
 from natsort import index_natsorted
@@ -1089,7 +1090,15 @@ def convert_excel_date(
     :param df: A pandas DataFrame.
     :param column_name: A column name.
     :returns: A pandas DataFrame with corrected dates.
+    :raises ValueError: if There are non numeric values in the column.
     """  # noqa: E501
+
+    if not is_numeric_dtype(df[column_name]):
+        raise ValueError(
+            "There are non-numeric values in the column. \
+    All values must be numeric"
+        )
+
     df[column_name] = pd.TimedeltaIndex(
         df[column_name], unit="d"
     ) + dt.datetime(

tests/functions/test_convert_excel_date.py

@@ -18,3 +18,15 @@ def test_convert_excel_date():
     )
 
     assert df["hire_date"].dtype == "M8[ns]"
+
+
+@pytest.mark.functions
+def test_convert_excel_date_with_string_data():
+    """ Raises ValueError if values of column are not numeric """
+    df = pd.read_excel(
+        Path(pytest.EXAMPLES_DIR) / "notebooks" / "dirty_data.xlsx",
+        engine="openpyxl",
+    ).clean_names()
+
+    with pytest.raises(ValueError):
+        df.convert_excel_date("hire_date_str")