DOC: added examples to DataFrame.std (#44226)

Author: ruankie

pandas/core/generic.py

@@ -10640,6 +10640,7 @@ def mad(self, axis=None, skipna=None, level=None):
             name2=name2,
             axis_descr=axis_descr,
             notes="",
+            examples="",
         )
         def sem(
             self,
@@ -10662,6 +10663,7 @@ def sem(
             name2=name2,
             axis_descr=axis_descr,
             notes="",
+            examples="",
         )
         def var(
             self,
@@ -10680,11 +10682,12 @@ def var(
             _num_ddof_doc,
             desc="Return sample standard deviation over requested axis."
             "\n\nNormalized by N-1 by default. This can be changed using the "
-            "ddof argument",
+            "ddof argument.",
             name1=name1,
             name2=name2,
             axis_descr=axis_descr,
             notes=_std_notes,
+            examples=_std_examples,
         )
         def std(
             self,
@@ -11176,7 +11179,8 @@ def _doc_params(cls):
 Returns
 -------
 {name1} or {name2} (if level specified) \
-{notes}
+{notes}\
+{examples}
 """
 
 _std_notes = """
@@ -11186,6 +11190,34 @@ def _doc_params(cls):
 To have the same behaviour as `numpy.std`, use `ddof=0` (instead of the
 default `ddof=1`)"""
 
+_std_examples = """
+
+Examples
+--------
+>>> df = pd.DataFrame({'person_id': [0, 1, 2, 3],
+...                   'age': [21, 25, 62, 43],
+...                   'height': [1.61, 1.87, 1.49, 2.01]}
+...                  ).set_index('person_id')
+>>> df
+           age  height
+person_id
+0           21    1.61
+1           25    1.87
+2           62    1.49
+3           43    2.01
+
+The standard deviation of the columns can be found as follows:
+
+>>> df.std()
+age       18.786076
+height     0.237417
+
+Alternatively, `ddof=0` can be set to normalize by N instead of N-1:
+
+>>> df.std(ddof=0)
+age       16.269219
+height     0.205609"""
+
 _bool_doc = """
 {desc}