DOC: Update the examples to DataFrame.mod docstring (pandas-dev#20406)

Author: ailchau

pandas/core/ops.py

@@ -401,6 +401,52 @@ def _get_op_name(op, special):
 e  NaN  -2.0
 """
 
+_mod_example_FRAME = """
+**Using a scalar argument**
+
+>>> df = pd.DataFrame([2, 4, np.nan, 6.2], index=["a", "b", "c", "d"],
+...                   columns=['one'])
+>>> df
+    one
+a   2.0
+b   4.0
+c   NaN
+d   6.2
+>>> df.mod(3, fill_value=-1)
+    one
+a   2.0
+b   1.0
+c   2.0
+d   0.2
+
+**Using a DataFrame argument**
+
+>>> df = pd.DataFrame(dict(one=[np.nan, 2, 3, 14], two=[np.nan, 1, 1, 3]),
+...                   index=['a', 'b', 'c', 'd'])
+>>> df
+    one   two
+a   NaN   NaN
+b   2.0   1.0
+c   3.0   1.0
+d   14.0  3.0
+>>> other = pd.DataFrame(dict(one=[np.nan, np.nan, 6, np.nan],
+...                           three=[np.nan, 10, np.nan, -7]),
+...                      index=['a', 'b', 'd', 'e'])
+>>> other
+    one three
+a   NaN NaN
+b   NaN 10.0
+d   6.0 NaN
+e   NaN -7.0
+>>> df.mod(other, fill_value=3)
+    one   three two
+a   NaN   NaN   NaN
+b   2.0   3.0   1.0
+c   0.0   NaN   1.0
+d   2.0   NaN   0.0
+e   NaN  -4.0   NaN
+"""
+
 _op_descriptions = {
     # Arithmetic Operators
     'add': {'op': '+',
@@ -418,7 +464,7 @@ def _get_op_name(op, special):
     'mod': {'op': '%',
             'desc': 'Modulo',
             'reverse': 'rmod',
-            'df_examples': None},
+            'df_examples': _mod_example_FRAME},
     'pow': {'op': '**',
             'desc': 'Exponential power',
             'reverse': 'rpow',