DOC: update the DataFrame.update() docstring

pandas/core/frame.py

@@ -4321,21 +4321,41 @@ def combiner(x, y, needs_i8_conversion=False):
     def update(self, other, join='left', overwrite=True, filter_func=None,
                raise_conflict=False):
         """
-        Modify DataFrame in place using non-NA values from passed
-        DataFrame. Aligns on indices
+        Modify in place using non-NA values from another DataFrame.
+
+        Aligns on indices. There is no return value.
 
         Parameters
         ----------
         other : DataFrame, or object coercible into a DataFrame
+            Index should be similar to one of the columns in this one. If a
+            Series is passed, its name attribute must be set, and that will be
+            used as the column name in the resulting joined DataFrame.
         join : {'left'}, default 'left'
+            Only left join is implemented, keeping the index and columns of the
+            original object.
         overwrite : boolean, default True
-            If True then overwrite values for common keys in the calling frame
+            How to handle non-NA values for overlapping keys.
+
+            * True : overwrite values in `self` with values from `other`.
+            * False : only update values that are NA in `self`.
+
         filter_func : callable(1d-array) -> 1d-array<boolean>, default None
             Can choose to replace values other than NA. Return True for values
-            that should be updated
+            that should be updated.
         raise_conflict : boolean
-            If True, will raise an error if the DataFrame and other both
-            contain data in the same place.
+            If True, will raise a `ValueError` if the DataFrame and `other`
+            both contain non-NA data in the same place.
+
+        Raises
+        ------
+        ValueError
+            When `raise_conflict` is True and there's overlapping non-NA data.
+
+        See Also
+        --------
+        dict.update : Similar method for dictionaries.
+        DataFrame.merge : For column(s)-on-columns(s) operations.
 
         Examples
         --------
@@ -4350,6 +4370,8 @@ def update(self, other, join='left', overwrite=True, filter_func=None,
         1  2  5
         2  3  6
 
+        The DataFrame's length does not increase as a result of the update.
+
         >>> df = pd.DataFrame({'A': ['a', 'b', 'c'],
         ...                    'B': ['x', 'y', 'z']})
         >>> new_df = pd.DataFrame({'B': ['d', 'e', 'f', 'g', 'h', 'i']})
@@ -4360,6 +4382,8 @@ def update(self, other, join='left', overwrite=True, filter_func=None,
         1  b  e
         2  c  f
 
+        For Series, it's name attribute must be set.
+
         >>> df = pd.DataFrame({'A': ['a', 'b', 'c'],
         ...                    'B': ['x', 'y', 'z']})
         >>> new_column = pd.Series(['d', 'e'], name='B', index=[0, 2])