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DOC: update str.cat example #23723

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merged 11 commits into from
Jan 4, 2019
23 changes: 15 additions & 8 deletions doc/source/text.rst
Original file line number Diff line number Diff line change
Expand Up @@ -306,23 +306,30 @@ The same alignment can be used when ``others`` is a ``DataFrame``:
Concatenating a Series and many objects into a Series
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

All one-dimensional list-likes can be combined in a list-like container (including iterators, ``dict``-views, etc.):
Several items can be combined a list-like container (including iterators, ``dict``-views, etc.), which may contain ``Series``, ``Index`` and ``np.ndarray``.
Note that ``Index`` will align as well, so for the purpose of this example, we change ``s`` and ``u`` from above to also have a string index:

.. ipython:: python

s
u
s.str.cat([u.values,
u.index.astype(str).values], na_rep='-')
s_values = np.array(['a', 'b', 'c', 'd'], dtype=object)
s2 = pd.Series(s_values, index=s_values)
s2
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add this in multiple blocks as its too much to complicated here

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this whole example needs to be simpler. maybe just leave the index as integers to avoid confusion, IOW focus less on the join in str.cat and more on the list-lke things that are going on.

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The thing this example tries to show is that it works for Series, ndarray, and Index, and Index can only be aligned with a non-integer index. This whole example would be so so much easier with #22225. I've opened an issue for the DF discussion a while ago, and asked you to comment #24046.

u_values = np.array(['b', 'd', 'a', 'c'], dtype=object)
u2 = pd.Series(u_values, index=u_values)
u2
idx = pd.Index(['d', 'c', 'b', 'a'])
idx
s2.str.cat([u2, idx, u_values], join='left')

All elements must match in length to the calling ``Series`` (or ``Index``), except those having an index if ``join`` is not None:
All ``np.ndarrays`` within the passed list-like must match in length to the calling ``Series`` (or ``Index``),
but ``Series`` and ``Index`` may have arbitrary length (as long as alignment is not disabled with ``join is not None``):

.. ipython:: python

v
s.str.cat([u, v], join='outer', na_rep='-')
s.str.cat([v, u, u_values], join='outer', na_rep='-')

If using ``join='right'`` on a list of ``others`` that contains different indexes,
If using ``join='right'`` on a list-like of ``others`` that contains different indexes,
the union of these indexes will be used as the basis for the final concatenation:

.. ipython:: python
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