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DOC: add examples to get_indexer_non_unique #50152

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Dec 10, 2022
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DOC: add examples to get_indexer_non_unique #50152

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DOC: add examples to get_indexer_non_unique
natmokval Dec 9, 2022
27b9ff0
DOC: add examples to get_indexer_non_unique II
natmokval Dec 10, 2022
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DOC: add examples to get_indexer_non_unique III
natmokval Dec 10, 2022
3d660b1
Update pandas/core/indexes/base.py
MarcoGorelli Dec 10, 2022
ef7c4e8
Update pandas/core/indexes/base.py
MarcoGorelli Dec 10, 2022
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19 changes: 19 additions & 0 deletions pandas/core/indexes/base.py
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Original file line number Diff line number Diff line change
Expand Up @@ -5557,6 +5557,25 @@ def _should_fallback_to_positional(self) -> bool:
missing : np.ndarray[np.intp]
An indexer into the target of the values not found.
These correspond to the -1 in the indexer array.

Examples
--------
>>> index = pd.Index(['c', 'b', 'a', 'b', 'b'])
>>> index.get_indexer_non_unique(['f', 'b', 's'])
(array([-1, 1, 3, 4, -1]), array([0, 2]))

>>> index = pd.Index(['c', 'b', 'a', 'b', 'b'])
>>> index.get_indexer_non_unique(['b', 'b'])
(array([1, 3, 4, 1, 3, 4]), array([], dtype=int64))
Comment on lines +5563 to +5565
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can we give this example first?

and then have the examples with missing values

Apart from the first example, can we also have a sentence before the missing values one, describing what the example is demonstrating?

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can we give this example first?

and then have the examples with missing values

Certainly. I will change the order of examples as you suggested.

Apart from the first example, can we also have a sentence before the missing values one, describing what the example is demonstrating?

Adding a sentence before the example with missing values sounds like a great idea.

To make this example more understandable I suggest the following explanation :
In the example below there are no matched values. For this reason, the returned indexer contains only integers equal to -1. It demonstrates no index at these positions that match the corresponding target values. The mask [0, 1, 2] in the return value shows that the first, second, and third elements are missing.

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yeah looks fine


>>> index = pd.Index(['c', 'b', 'a', 'b', 'b'])
>>> index.get_indexer_non_unique(['q', 'r', 't'])
(array([-1, -1, -1]), array([0, 1, 2]))

Notice that the return value is a tuple contains two items.
The first item is an array of locations in ``index`` and ``x``
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what's x?

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My mistake, there is no x in my examples ;) In this example, it should be q, r, and t.

is marked by -1, as it is not in ``index``. The second item
is a mask for new index given the current index.
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not sure we need to repeat the return description here - perhaps, describe the mask given the example? e.g. given that the first and third elements are missing, the mask shows [0, 2]

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agreed, there is no need to repeat return sentence. I will add an explanation of what the mask shows.

"""

@Appender(_index_shared_docs["get_indexer_non_unique"] % _index_doc_kwargs)
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