diff --git a/pandas/core/indexing.py b/pandas/core/indexing.py index a69313a2d4a43..80396a9149d5a 100755 --- a/pandas/core/indexing.py +++ b/pandas/core/indexing.py @@ -1924,7 +1924,8 @@ def _getitem_axis(self, key, axis=None): class _iLocIndexer(_LocationIndexer): - """Purely integer-location based indexing for selection by position. + """ + Purely integer-location based indexing for selection by position. ``.iloc[]`` is primarily integer position based (from ``0`` to ``length-1`` of the axis), but may also be used with a boolean @@ -1937,14 +1938,125 @@ class _iLocIndexer(_LocationIndexer): - A slice object with ints, e.g. ``1:7``. - A boolean array. - A ``callable`` function with one argument (the calling Series, DataFrame - or Panel) and that returns valid output for indexing (one of the above) + or Panel) and that returns valid output for indexing (one of the above). + This is useful in method chains, when you don't have a reference to the + calling object, but would like to base your selection on some value. ``.iloc`` will raise ``IndexError`` if a requested indexer is out-of-bounds, except *slice* indexers which allow out-of-bounds indexing (this conforms with python/numpy *slice* semantics). - See more at :ref:`Selection by Position ` + See more at ref:`Selection by Position `. + + See Also + -------- + DataFrame.iat : Fast integer location scalar accessor. + DataFrame.loc : Purely label-location based indexer for selection by label. + Series.iloc : Purely integer-location based indexing for + selection by position. + + Examples + -------- + + >>> mydict = [{'a': 1, 'b': 2, 'c': 3, 'd': 4}, + ... {'a': 100, 'b': 200, 'c': 300, 'd': 400}, + ... {'a': 1000, 'b': 2000, 'c': 3000, 'd': 4000 }] + >>> df = pd.DataFrame(mydict) + >>> df + a b c d + 0 1 2 3 4 + 1 100 200 300 400 + 2 1000 2000 3000 4000 + + **Indexing just the rows** + + With a scalar integer. + + >>> type(df.iloc[0]) + + >>> df.iloc[0] + a 1 + b 2 + c 3 + d 4 + Name: 0, dtype: int64 + + With a list of integers. + + >>> df.iloc[[0]] + a b c d + 0 1 2 3 4 + >>> type(df.iloc[[0]]) + + + >>> df.iloc[[0, 1]] + a b c d + 0 1 2 3 4 + 1 100 200 300 400 + + With a `slice` object. + + >>> df.iloc[:3] + a b c d + 0 1 2 3 4 + 1 100 200 300 400 + 2 1000 2000 3000 4000 + + With a boolean mask the same length as the index. + + >>> df.iloc[[True, False, True]] + a b c d + 0 1 2 3 4 + 2 1000 2000 3000 4000 + + With a callable, useful in method chains. The `x` passed + to the ``lambda`` is the DataFrame being sliced. This selects + the rows whose index label even. + + >>> df.iloc[lambda x: x.index % 2 == 0] + a b c d + 0 1 2 3 4 + 2 1000 2000 3000 4000 + + **Indexing both axes** + + You can mix the indexer types for the index and columns. Use ``:`` to + select the entire axis. + + With scalar integers. + + >>> df.iloc[0, 1] + 2 + + With lists of integers. + + >>> df.iloc[[0, 2], [1, 3]] + b d + 0 2 4 + 2 2000 4000 + + With `slice` objects. + + >>> df.iloc[1:3, 0:3] + a b c + 1 100 200 300 + 2 1000 2000 3000 + + With a boolean array whose length matches the columns. + + >>> df.iloc[:, [True, False, True, False]] + a c + 0 1 3 + 1 100 300 + 2 1000 3000 + + With a callable function that expects the Series or DataFrame. + >>> df.iloc[:, lambda df: [0, 2]] + a c + 0 1 3 + 1 100 300 + 2 1000 3000 """ _valid_types = ("integer, integer slice (START point is INCLUDED, END "