DOC: Improve the docstring of pandas.DataFrame.append() (pandas-dev#20267)

Author: Triple0

pandas/core/frame.py

@@ -145,8 +145,11 @@
 
 Parameters
 ----------%s
-right : DataFrame
+right : DataFrame, Series or dict
+    Object to merge with.
 how : {'left', 'right', 'outer', 'inner'}, default 'inner'
+    Type of merge to be performed.
+
     * left: use only keys from left frame, similar to a SQL left outer join;
       preserve key order
     * right: use only keys from right frame, similar to a SQL right outer join;
@@ -170,18 +173,18 @@
 left_index : boolean, default False
     Use the index from the left DataFrame as the join key(s). If it is a
     MultiIndex, the number of keys in the other DataFrame (either the index
-    or a number of columns) must match the number of levels
+    or a number of columns) must match the number of levels.
 right_index : boolean, default False
     Use the index from the right DataFrame as the join key. Same caveats as
-    left_index
+    left_index.
 sort : boolean, default False
     Sort the join keys lexicographically in the result DataFrame. If False,
-    the order of the join keys depends on the join type (how keyword)
+    the order of the join keys depends on the join type (how keyword).
 suffixes : 2-length sequence (tuple, list, ...)
     Suffix to apply to overlapping column names in the left and right
-    side, respectively
+    side, respectively.
 copy : boolean, default True
-    If False, do not copy data unnecessarily
+    If False, avoid copy if possible.
 indicator : boolean or string, default False
     If True, adds a column to output DataFrame called "_merge" with
     information on the source of each row.
@@ -205,41 +208,49 @@
 
     .. versionadded:: 0.21.0
 
+Returns
+-------
+DataFrame
+
 Notes
 -----
 Support for specifying index levels as the `on`, `left_on`, and
 `right_on` parameters was added in version 0.23.0
 
+See Also
+--------
+merge_ordered : merge with optional filling/interpolation.
+merge_asof : merge on nearest keys.
+DataFrame.join : similar method using indices.
+
 Examples
 --------
 
->>> A              >>> B
-    lkey value         rkey value
-0   foo  1         0   foo  5
-1   bar  2         1   bar  6
-2   baz  3         2   qux  7
-3   foo  4         3   bar  8
+>>> A = pd.DataFrame({'lkey': ['foo', 'bar', 'baz', 'foo'],
+...                   'value': [1, 2, 3, 5]})
+>>> B = pd.DataFrame({'rkey': ['foo', 'bar', 'baz', 'foo'],
+...                   'value': [5, 6, 7, 8]})
+>>> A
+    lkey value
+0   foo      1
+1   bar      2
+2   baz      3
+3   foo      5
+>>> B
+    rkey value
+0   foo      5
+1   bar      6
+2   baz      7
+3   foo      8
 
 >>> A.merge(B, left_on='lkey', right_on='rkey', how='outer')
-   lkey  value_x  rkey  value_y
-0  foo   1        foo   5
-1  foo   4        foo   5
-2  bar   2        bar   6
-3  bar   2        bar   8
-4  baz   3        NaN   NaN
-5  NaN   NaN      qux   7
-
-Returns
--------
-merged : DataFrame
-    The output type will the be same as 'left', if it is a subclass
-    of DataFrame.
-
-See also
---------
-merge_ordered
-merge_asof
-DataFrame.join
+  lkey  value_x rkey  value_y
+0  foo        1  foo        5
+1  foo        1  foo        8
+2  foo        5  foo        5
+3  foo        5  foo        8
+4  bar        2  bar        6
+5  baz        3  baz        7
 """
 
 # -----------------------------------------------------------------------
@@ -3244,14 +3255,15 @@ def insert(self, loc, column, value, allow_duplicates=False):
 
     def assign(self, **kwargs):
         r"""
-        Assign new columns to a DataFrame, returning a new object
-        (a copy) with the new columns added to the original ones.
+        Assign new columns to a DataFrame.
+
+        Returns a new object with all original columns in addition to new ones.
         Existing columns that are re-assigned will be overwritten.
 
         Parameters
         ----------
         kwargs : keyword, value pairs
-            keywords are the column names. If the values are
+            The column names are keywords. If the values are
             callable, they are computed on the DataFrame and
             assigned to the new columns. The callable must not
             change input DataFrame (though pandas doesn't check it).
@@ -3276,7 +3288,7 @@ def assign(self, **kwargs):
 
         .. versionchanged :: 0.23.0
 
-            Keyword argument order is maintained for Python 3.6 and later.
+           Keyword argument order is maintained for Python 3.6 and later.
 
         Examples
         --------
@@ -6250,8 +6262,9 @@ def infer(x):
     def append(self, other, ignore_index=False,
                verify_integrity=False, sort=None):
         """
-        Append rows of `other` to the end of this frame, returning a new
-        object. Columns not in this frame are added as new columns.
+        Append rows of `other` to the end of caller, returning a new object.
+
+        Columns in `other` that are not in the caller are added as new columns.
 
         Parameters
         ----------
@@ -6341,7 +6354,6 @@ def append(self, other, ignore_index=False,
         2  2
         3  3
         4  4
-
         """
         if isinstance(other, (Series, dict)):
             if isinstance(other, dict):
@@ -6611,7 +6623,6 @@ def round(self, decimals=0, *args, **kwargs):
         --------
         numpy.around
         Series.round
-
         """
         from pandas.core.reshape.concat import concat