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DOC: formatting adjustments, ensure DType classes show up in API docs
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ngoldbaum committed Dec 28, 2023
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8 changes: 7 additions & 1 deletion doc/source/reference/routines.other.rst
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Expand Up @@ -33,4 +33,10 @@ Utility
show_runtime
broadcast_shapes

.. automodule:: numpy.dtypes
DType classes and utility (:mod:`numpy.dtypes`)
===============================================

.. autosummary::
:toctree: generated/

dtypes
64 changes: 35 additions & 29 deletions doc/source/user/basics.types.rst
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Expand Up @@ -12,10 +12,10 @@ Array types and conversions between types
NumPy supports a much greater variety of numerical types than Python does.
This section shows which are available, and how to modify an array's data-type.

NumPy numerical types are instances of ``dtype`` (data-type) objects, each
having unique characteristics. Once you have imported NumPy using
``>>> import numpy as np``
the dtypes are available as ``np.bool``, ``np.float32``, etc.
NumPy numerical types are instances of `numpy.dtype` (data-type) objects,
each having unique characteristics. Once you have imported NumPy using ``import
numpy as np`` the dtypes are available as e.g. `numpy.bool`,
`numpy.float32`, etc.

Data-types can be used as functions to convert python numbers to array scalars
(see the array scalar section for an explanation), python sequences of numbers
Expand All @@ -33,8 +33,9 @@ functions or methods accept. Some examples::
array([0, 1, 2], dtype=uint8)

Array types can also be referred to by character codes, mostly to retain
backward compatibility with older packages such as Numeric. Some
documentation may still refer to these, for example::
backward compatibility with older packages such as Numeric, but also for
defining :ref:`structured data types <structured_arrays>`. Some
documentation may refer to these character codes, for example::

>>> np.array([1, 2, 3], dtype='f')
array([1., 2., 3.], dtype=float32)
Expand All @@ -49,10 +50,11 @@ the type itself as a function. For example: ::
>>> np.int8(z)
array([0, 1, 2], dtype=int8)

Note that, above, we use the *Python* float object as a dtype. NumPy knows
that ``int`` refers to ``np.int_``, ``bool`` means ``np.bool``,
that ``float`` is ``np.float64`` and ``complex`` is ``np.complex128``.
The other data-types do not have Python equivalents.
Note that, above, we use the *Python* float object as a dtype. NumPy knows that
:class:`int` refers to `numpy.int_`, :class:`bool` means
`numpy.bool`, that :class:`float` is `numpy.float64` and
:class:`complex` is `numpy.complex128`. The other data-types do not have
Python equivalents.

To determine the type of an array, look at the dtype attribute::

Expand All @@ -76,21 +78,24 @@ properties of the type, such as whether it is an integer::
Numerical Data Types
--------------------

There are 5 basic numerical types representing booleans (bool), integers (int),
unsigned integers (uint) floating point (float) and complex. Those with numbers
in their name indicate the bitsize of the type (i.e. how many bits are needed
to represent a single value in memory). Some types, such as ``int`` and
``intp``, have differing bitsizes, dependent on the platforms (e.g. 32-bit
vs. 64-bit machines). This should be taken into account when interfacing
with low-level code (such as C or Fortran) where the raw memory is addressed.
There are 5 basic numerical types representing booleans (``bool``), integers
(``int``), unsigned integers (``uint``) floating point (``float``) and
``complex``. A basic numerical type name combined with a numeric bitsize defines
a concrete type. The bitsize is the number of bits that are needed to represent
a single value in memory. For example, `numpy.float64` is a 64 bit
floating point data type. Some types, such as `numpy.int` and
`numpy.intp`, have differing bitsizes, dependent on the platforms
(e.g. 32-bit vs. 64-bit CPU architectures). This should be taken into account
when interfacing with low-level code (such as C or Fortran) where the raw memory
is addressed.

Data Types for Strings and Bytes
--------------------------------

In addition to numerical types, NumPy also supports storing unicode strings, via
`np.dtypes.StrDtype` (``U`` character code), null-terminated byte sequences via
`np.dtypes.BytesDType` (``S`` character code), and arbitrary byte sequences, via
`np.dtypes.VoidDType` (``V`` character code).
`numpy.dtypes.StrDType` (``U`` character code), null-terminated byte sequences via
`numpy.dtypes.BytesDType` (``S`` character code), and arbitrary byte sequences, via
`numpy.dtypes.VoidDType` (``V`` character code).

The ``StrDType``, ``BytesDType``, and ``VoidDType`` are *fixed-width* data
types. They are parameterized by a width, in either bytes or unicode points,
Expand Down Expand Up @@ -294,7 +299,8 @@ exceptions, such as when code requires very specific attributes of a scalar
or when it checks specifically whether a value is a Python scalar. Generally,
problems are easily fixed by explicitly converting array scalars
to Python scalars, using the corresponding Python type function
(e.g., ``int``, ``float``, ``complex``, ``str``, ``unicode``).
(e.g., :class:`int`, :class:`float`, :class:`complex`, :class:`str`,
:class:`unicode`).

The primary advantage of using array scalars is that
they preserve the array type (Python may not have a matching scalar type
Expand All @@ -320,9 +326,9 @@ but gives -1486618624 (incorrect) for a 32-bit integer.

The behaviour of NumPy and Python integer types differs significantly for
integer overflows and may confuse users expecting NumPy integers to behave
similar to Python's ``int``. Unlike NumPy, the size of Python's ``int`` is
flexible. This means Python integers may expand to accommodate any integer and
will not overflow.
similar to Python's :class:`int`. Unlike NumPy, the size of Python's
:class:`int` is flexible. This means Python integers may expand to accommodate
any integer and will not overflow.

NumPy provides `numpy.iinfo` and `numpy.finfo` to verify the
minimum or maximum values of NumPy integer and floating point values
Expand All @@ -348,22 +354,22 @@ Extended precision
==================

Python's floating-point numbers are usually 64-bit floating-point numbers,
nearly equivalent to ``np.float64``. In some unusual situations it may be
nearly equivalent to `numpy.float64`. In some unusual situations it may be
useful to use floating-point numbers with more precision. Whether this
is possible in numpy depends on the hardware and on the development
environment: specifically, x86 machines provide hardware floating-point
with 80-bit precision, and while most C compilers provide this as their
``long double`` type, MSVC (standard for Windows builds) makes
``long double`` identical to ``double`` (64 bits). NumPy makes the
compiler's ``long double`` available as ``np.longdouble`` (and
compiler's ``long double`` available as `numpy.longdouble` (and
``np.clongdouble`` for the complex numbers). You can find out what your
numpy provides with ``np.finfo(np.longdouble)``.

NumPy does not provide a dtype with more precision than C's
``long double``; in particular, the 128-bit IEEE quad precision
data type (FORTRAN's ``REAL*16``) is not available.

For efficient memory alignment, ``np.longdouble`` is usually stored
For efficient memory alignment, `numpy.longdouble` is usually stored
padded with zero bits, either to 96 or 128 bits. Which is more efficient
depends on hardware and development environment; typically on 32-bit
systems they are padded to 96 bits, while on 64-bit systems they are
Expand All @@ -374,8 +380,8 @@ want specific padding. In spite of the names, ``np.float96`` and
that is, 80 bits on most x86 machines and 64 bits in standard
Windows builds.

Be warned that even if ``np.longdouble`` offers more precision than
python ``float``, it is easy to lose that extra precision, since
Be warned that even if `numpy.longdouble` offers more precision than
python :class:`float`, it is easy to lose that extra precision, since
python often forces values to pass through ``float``. For example,
the ``%`` formatting operator requires its arguments to be converted
to standard python types, and it is therefore impossible to preserve
Expand Down
7 changes: 2 additions & 5 deletions numpy/dtypes.py
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@@ -1,7 +1,4 @@
"""
DType classes and utility (:mod:`numpy.dtypes`)
===============================================
This module is home to specific dtypes related functionality and their classes.
For more general information about dtypes, also see `numpy.dtype` and
:ref:`arrays.dtypes`.
Expand Down Expand Up @@ -49,8 +46,8 @@
* - Complex
- ``Complex64DType``, ``Complex128DType``, ``CLongDoubleDType``
* - Strings
- ``BytesDType``, ``BytesDType``
* - Strings and Bytestrings
- ``StrDType``, ``BytesDType``
* - Times
- ``DateTime64DType``, ``TimeDelta64DType``
Expand Down

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