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Diffstat (limited to 'doc/source/reference/arrays.indexing.rst')
| -rw-r--r-- | doc/source/reference/arrays.indexing.rst | 24 |
1 files changed, 12 insertions, 12 deletions
diff --git a/doc/source/reference/arrays.indexing.rst b/doc/source/reference/arrays.indexing.rst index 000a06def..a47474922 100644 --- a/doc/source/reference/arrays.indexing.rst +++ b/doc/source/reference/arrays.indexing.rst @@ -14,8 +14,8 @@ Indexing There are three kinds of indexing available: record access, basic slicing, advanced indexing. Which one occurs depends on *obj*. -.. note:: - +.. note:: + In Python, ``x[(exp1, exp2, ..., expN)]`` is equivalent to ``x[exp1, exp2, ..., expN]``; the latter is just syntactic sugar for the former. @@ -151,7 +151,7 @@ concepts to remember include: .. warning:: The above is **not** true for advanced slicing. - You may use slicing to set values in the array, but (unlike lists) you - can never grow the array. The size of the value to be set in + can never grow the array. The size of the value to be set in ``x[obj] = value`` must be (broadcastable) to the same shape as ``x[obj]``. @@ -169,7 +169,7 @@ concepts to remember include: of arbitrary dimension. .. data:: newaxis - + The :const:`newaxis` object can be used in the basic slicing syntax discussed above. :const:`None` can also be used instead of :const:`newaxis`. @@ -182,7 +182,7 @@ Advanced indexing is triggered when the selection object, *obj*, is a non-tuple sequence object, an :class:`ndarray` (of data type integer or bool), or a tuple with at least one sequence object or ndarray (of data type integer or bool). There are two types of advanced indexing: integer -and Boolean. +and Boolean. Advanced indexing always returns a *copy* of the data (contrast with basic slicing that returns a :term:`view`). @@ -200,7 +200,7 @@ tuple. The rules of advanced integer-style indexing are: - If the length of the selection tuple is larger than *N* an error is raised. -- All sequences and scalars in the selection tuple are converted to +- All sequences and scalars in the selection tuple are converted to :class:`intp` indexing arrays. - All selection tuple objects must be convertible to :class:`intp` @@ -221,7 +221,7 @@ tuple. The rules of advanced integer-style indexing are: - The shape of the output (or the needed shape of the object to be used for setting) is the broadcasted shape. - + - After expanding any ellipses and filling out any missing ``:`` objects in the selection tuple, then let :math:`N_t` be the number of indexing arrays, and let :math:`N_s = N - N_t` be the number of @@ -230,9 +230,9 @@ tuple. The rules of advanced integer-style indexing are: - If :math:`N_s = 0` then the *M*-dimensional result is constructed by varying the index tuple ``(i_1, ..., i_M)`` over the range - of the result shape and for each value of the index tuple + of the result shape and for each value of the index tuple ``(ind_1, ..., ind_M)``:: - + result[i_1, ..., i_M] == x[ind_1[i_1, ..., i_M], ind_2[i_1, ..., i_M], ..., ind_N[i_1, ..., i_M]] @@ -244,7 +244,7 @@ tuple. The rules of advanced integer-style indexing are: *i, j, k* yields:: result[i,j,k] = x[ind_1[i,j,k], ind_2[i,j,k]] - + - If :math:`N_s > 0`, then partial indexing is done. This can be somewhat mind-boggling to understand, but if you think in terms of the shapes of the arrays involved, it can be easier to grasp what @@ -269,7 +269,7 @@ tuple. The rules of advanced integer-style indexing are: we let *i, j, k* loop over the (2,3,4)-shaped subspace then ``result[...,i,j,k,:] = x[...,ind[i,j,k],:]``. This example produces the same result as :meth:`x.take(ind, axis=-2) <ndarray.take>`. - + .. admonition:: Example Now let ``x.shape`` be (10,20,30,40,50) and suppose ``ind_1`` @@ -305,7 +305,7 @@ bounds of *x*, then an index error will be raised. You can also use Boolean arrays as element of the selection tuple. In such instances, they will always be interpreted as :meth:`nonzero(obj) <ndarray.nonzero>` and the equivalent integer indexing will be -done. +done. .. warning:: |