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authorJim Turner <git@turner.link>2018-12-11 14:40:14 -0500
committerJim Turner <git@turner.link>2018-12-12 12:39:00 -0500
commit8eefc53ac9cfcd4ccc5b70ccfc900b06b389dce3 (patch)
tree969626cb6e5d0bdd7566bde9554faddf8191c48f
parentb40321f0668673c0519ce0e124427cb8d0cc3135 (diff)
downloadnumpy-8eefc53ac9cfcd4ccc5b70ccfc900b06b389dce3.tar.gz
DOC: Fix desc. of Ellipsis behavior in reference
`Ellipsis` expands to make the selection tuple be consistent with the number of dimensions of the array being indexed. The length of the expanded selection tuple may not be equal to the number of dimensions in the array due to `newaxis` objects or advanced indexing. This commit fixes the docs to correctly explain the behavior of `Ellipsis`. For example, ```python >>> import numpy as np >>> x = np.zeros((3, 3, 3)) >>> x[:, ..., :2, np.newaxis].shape (3, 3, 2, 1) >>> x[:, :, :2, np.newaxis].shape (3, 3, 2, 1) ``` The `Ellipsis` expands to a single `:` so that the selection tuple can index the 3-D array. The length of the expanded selection tuple is 4, not 3 as the docs indicated before this commit.
-rw-r--r--doc/source/reference/arrays.indexing.rst7
1 files changed, 4 insertions, 3 deletions
diff --git a/doc/source/reference/arrays.indexing.rst b/doc/source/reference/arrays.indexing.rst
index 62d36e28c..5f67a788a 100644
--- a/doc/source/reference/arrays.indexing.rst
+++ b/doc/source/reference/arrays.indexing.rst
@@ -111,9 +111,10 @@ concepts to remember include:
[5],
[6]]])
-- :const:`Ellipsis` expand to the number of ``:`` objects needed to
- make a selection tuple of the same length as ``x.ndim``. There may
- only be a single ellipsis present.
+- :const:`Ellipsis` expands to the number of ``:`` objects needed for the
+ selection tuple to index all dimensions. In most cases, this means that
+ length of the expanded selection tuple is ``x.ndim``. There may only be a
+ single ellipsis present.
.. admonition:: Example