NumPy v1.19.0.rc1 Release Notes

Release Date: 2020-05-18 // almost 4 years ago
  • ๐Ÿš€ NumPy 1.19.0 Release Notes

    ๐Ÿš€ This NumPy release is marked by the removal of much technical debt:
    ๐Ÿ‘Œ support for Python 2 has been removed, many deprecations have been
    ๐Ÿ“š expired, and documentation has been improved. The polishing of the
    ๐Ÿ›  random module continues apace with bug fixes and better usability from
    Cython.

    ๐Ÿš€ The Python versions supported for this release are 3.6-3.8. Downstream
    ๐Ÿ‘ developers should use Cython >= 0.29.16 for Python 3.8 support and
    OpenBLAS >= 3.7 to avoid problems on the Skylake architecture.

    Highlights

    Code compatibility with Python versions < 3.5 (including Python 2)
    was dropped from both the python and C code. The shims in
    ๐Ÿ“ฆ numpy.compat will remain to support third-party packages, but they
    ๐Ÿš€ may be deprecated in a future release.

    (gh-15233)

    ๐Ÿ—„ Expired deprecations

    numpy.insert and numpy.delete can no longer be passed an axis on 0d arrays

    ๐Ÿ—„ This concludes a deprecation from 1.9, where when an axis argument was
    passed to a call to ~numpy.insert and ~numpy.delete on a 0d array,
    the axis and obj argument and indices would be completely ignored.
    In these cases, insert(arr, "nonsense", 42, axis=0) would actually
    overwrite the entire array, while delete(arr, "nonsense", axis=0)
    would be arr.copy()

    Now passing axis on a 0d array raises ~numpy.AxisError.

    (gh-15802)

    numpy.delete no longer ignores out-of-bounds indices

    ๐Ÿ—„ This concludes deprecations from 1.8 and 1.9, where np.delete would
    ignore both negative and out-of-bounds items in a sequence of indices.
    This was at odds with its behavior when passed a single index.

    Now out-of-bounds items throw IndexError, and negative items index
    from the end.

    (gh-15804)

    numpy.insert and numpy.delete no longer accept non-integral indices

    ๐Ÿ—„ This concludes a deprecation from 1.9, where sequences of non-integers
    indices were allowed and cast to integers. Now passing sequences of
    non-integral indices raises IndexError, just like it does when passing
    a single non-integral scalar.

    (gh-15805)

    numpy.delete no longer casts boolean indices to integers

    ๐Ÿ—„ This concludes a deprecation from 1.8, where np.delete would cast
    boolean arrays and scalars passed as an index argument into integer
    indices. The behavior now is to treat boolean arrays as a mask, and to
    raise an error on boolean scalars.

    (gh-15815)

    Compatibility notes

    ๐Ÿ”„ Changed random variate stream from numpy.random.Generator.dirichlet

    A bug in the generation of random variates for the Dirichlet
    ๐Ÿ›  distribution with small 'alpha' values was fixed by using a different
    algorithm when max(alpha) < 0.1. Because of the change, the stream of
    variates generated by dirichlet in this case will be different from
    ๐Ÿš€ previous releases.

    (gh-14924)

    Scalar promotion in PyArray_ConvertToCommonType

    The promotion of mixed scalars and arrays in
    PyArray_ConvertToCommonType has been changed to adhere to those used
    by np.result_type. This means that input such as
    (1000, np.array([1], dtype=np.uint8))) will now return uint16
    dtypes. In most cases the behaviour is unchanged. Note that the use of
    ๐Ÿ›  this C-API function is generally discouraged. This also fixes
    np.choose to behave the same way as the rest of NumPy in this respect.

    (gh-14933)

    ๐Ÿ—„ Fasttake and fastputmask slots are deprecated and NULL'ed

    The fasttake and fastputmask slots are now never used and must always be
    set to NULL. This will result in no change in behaviour. However, if a
    ๐Ÿ—„ user dtype should set one of these a DeprecationWarning will be given.

    (gh-14942)

    np.ediff1d casting behaviour with to_end and to_begin

    np.ediff1d now uses the "same_kind" casting rule for its additional
    to_end and to_begin arguments. This ensures type safety except when
    the input array has a smaller integer type than to_begin or to_end.
    In rare cases, the behaviour will be more strict than it was previously
    in 1.16 and 1.17. This is necessary to solve issues with floating point
    NaN.

    (gh-14981)

    Converting of empty array-like objects to NumPy arrays

    Objects with len(obj) == 0 which implement an "array-like"
    interface, meaning an object implementing obj. __array__ (),
    obj. __array_interface__, obj. __array_struct__, or the python buffer
    interface and which are also sequences (i.e. Pandas objects) will now
    always retain there shape correctly when converted to an array. If such
    an object has a shape of (0, 1) previously, it could be converted into
    an array of shape (0,) (losing all dimensions after the first 0).

    (gh-14995)

    โœ‚ Removed multiarray.int_asbuffer

    As part of the continued removal of Python 2 compatibility,
    ๐Ÿšš multiarray.int_asbuffer was removed. On Python 3, it threw a
    NotImplementedError and was unused internally. It is expected that
    there are no downstream use cases for this method with Python 3.

    (gh-15229)

    ๐Ÿšš numpy.distutils.compat has been removed

    This module contained only the function get_exception(), which was
    ๐Ÿ‘‰ used as:

    try:
        ...
    except Exception:
        e = get_exception()
    

    Its purpose was to handle the change in syntax introduced in Python 2.6,
    ๐Ÿ‘ป from except Exception, e: to except Exception as e:, meaning it was
    ๐Ÿ‘ only necessary for codebases supporting Python 2.5 and older.

    (gh-15255)

    issubdtype no longer interprets float as np.floating

    โš  numpy.issubdtype had a FutureWarning since NumPy 1.14 which has
    expired now. This means that certain input where the second argument was
    neither a datatype nor a NumPy scalar type (such as a string or a python
    type like int or float) will now be consistent with passing in
    np.dtype(arg2).type. This makes the result consistent with
    expectations and leads to a false result in some cases which previously
    returned true.

    (gh-15773)

    ๐Ÿ”„ Change output of round on scalars to be consistent with Python

    Output of the __round__ dunder method and consequently the Python
    built-in round has been changed to be a Python int to be consistent
    with calling it on Python float objects when called with no arguments.
    Previously, it would return a scalar of the np.dtype that was passed
    in.

    (gh-15840)

    The numpy.ndarray constructor no longer interprets strides=() as strides=None

    The former has changed to have the expected meaning of setting
    numpy.ndarray.strides to (), while the latter continues to result in
    strides being chosen automatically.

    (gh-15882)

    C-Level string to datetime casts changed

    ๐Ÿ›  The C-level casts from strings were simplified. This changed also fixes
    string to datetime and timedelta casts to behave correctly (i.e. like
    Python casts using string_arr.astype("M8") while previously the cast
    would behave like string_arr.astype(np.int_).astype("M8"). This only
    affects code using low-level C-API to do manual casts (not full array
    casts) of single scalar values or using e.g. PyArray_GetCastFunc, and
    should thus not affect the vast majority of users.

    (gh-16068)

    ๐Ÿ—„ Deprecations

    ๐Ÿ—„ Deprecate automatic dtype=object for ragged input

    ๐Ÿ—„ Calling np.array([[1, [1, 2, 3]]) will issue a DeprecationWarning as
    per NEP 34. Users should
    โš  explicitly use dtype=object to avoid the warning.

    (gh-15119)

    ๐Ÿ—„ Passing shape=0 to factory functions in numpy.rec is deprecated

    0 is treated as a special case and is aliased to None in the
    functions:

    • numpy.core.records.fromarrays
    • numpy.core.records.fromrecords
    • numpy.core.records.fromstring
    • numpy.core.records.fromfile

    In future, 0 will not be special cased, and will be treated as an
    array length like any other integer.

    (gh-15217)

    ๐Ÿ—„ Deprecation of probably unused C-API functions

    The following C-API functions are probably unused and have been
    ๐Ÿ—„ deprecated:

    • PyArray_GetArrayParamsFromObject
    • PyUFunc_GenericFunction
    • PyUFunc_SetUsesArraysAsData

    In most cases PyArray_GetArrayParamsFromObject should be replaced by
    converting to an array, while PyUFunc_GenericFunction can be replaced
    ๐Ÿ“š with PyObject_Call (see documentation for details).

    (gh-15427)

    ๐Ÿ—„ Converting certain types to dtypes is Deprecated

    The super classes of scalar types, such as np.integer, np.generic,
    ๐Ÿ—„ or np.inexact will now give a deprecation warning when converted to a
    dtype (or used in a dtype keyword argument). The reason for this is that
    np.integer is converted to np.int_, while it would be expected to
    represent any integer (e.g. also int8, int16, etc. For example,
    dtype=np.floating is currently identical to dtype=np.float64, even
    though also np.float32 is a subclass of np.floating.

    (gh-15534)

    ๐Ÿ—„ Deprecation of round for np.complexfloating scalars

    Output of the __round__ dunder method and consequently the Python
    ๐Ÿ—„ built-in round has been deprecated on complex scalars. This does not
    affect np.round.

    (gh-15840)

    ๐Ÿ—„ numpy.ndarray.tostring() is deprecated in favor of tobytes()

    ๐Ÿš€ ~numpy.ndarray.tobytes has existed since the 1.9 release, but until
    ๐Ÿš€ this release ~numpy.ndarray.tostring emitted no warning. The change to
    โš  emit a warning brings NumPy in line with the builtin array.array
    methods of the same name.

    (gh-15867)

    C API changes

    ๐Ÿ‘ Better support for const dimensions in API functions

    The following functions now accept a constant array of npy_intp:

    • PyArray_BroadcastToShape
    • PyArray_IntTupleFromIntp
    • PyArray_OverflowMultiplyList

    Previously the caller would have to cast away the const-ness to call
    these functions.

    (gh-15251)

    Const qualify UFunc inner loops

    UFuncGenericFunction now expects pointers to const dimension and
    strides as arguments. This means inner loops may no longer modify
    either dimension or strides. This change leads to an
    โš  incompatible-pointer-types warning forcing users to either ignore the
    โš  compiler warnings or to const qualify their own loop signatures.

    (gh-15355)

    ๐Ÿ†• New Features

    numpy.frompyfunc now accepts an identity argument

    This allows the `numpy.ufunc.identity{.interpreted-text
    role="attr"}[ attribute to be set on the resulting ufunc, meaning it can
    be used for empty and multi-dimensional calls to
    :meth:]{.title-ref}[numpy.ufunc.reduce]{.title-ref}`.

    (gh-8255)

    ๐Ÿ‘ np.str_ scalars now support the buffer protocol

    np.str_ arrays are always stored as UCS4, so the corresponding scalars
    now expose this through the buffer interface, meaning
    โœ… memoryview(np.str_('test')) now works.

    (gh-15385)

    subok option for numpy.copy

    A new kwarg, subok, was added to numpy.copy to allow users to toggle
    the behavior of numpy.copy with respect to array subclasses. The
    0๏ธโƒฃ default value is False which is consistent with the behavior of
    numpy.copy for previous numpy versions. To create a copy that
    preserves an array subclass with numpy.copy, call
    ๐Ÿ‘ np.copy(arr, subok=True). This addition better documents that the
    0๏ธโƒฃ default behavior of numpy.copy differs from the numpy.ndarray.copy
    0๏ธโƒฃ method which respects array subclasses by default.

    (gh-15685)

    numpy.linalg.multi_dot now accepts an out argument

    out can be used to avoid creating unnecessary copies of the final
    product computed by numpy.linalg.multidot.

    (gh-15715)

    keepdims parameter for numpy.count_nonzero

    The parameter keepdims was added to numpy.count_nonzero. The
    parameter has the same meaning as it does in reduction functions such as
    numpy.sum or numpy.mean.

    (gh-15870)

    equal_nan parameter for numpy.array_equal

    The keyword argument equal_nan was added to numpy.array_equal.
    equal_nan is a boolean value that toggles whether or not nan values
    0๏ธโƒฃ are considered equal in comparison (default is False). This matches
    API used in related functions such as numpy.isclose and
    numpy.allclose.

    (gh-16128)

    ๐Ÿ‘Œ Improvements

    ๐Ÿ‘Œ Improve detection of CPU features

    Replace npy_cpu_supports which was a gcc specific mechanism to test
    support of AVX with more general functions npy_cpu_init and
    npy_cpu_have, and expose the results via a NPY_CPU_HAVE c-macro as
    well as a python-level __cpu_features__ dictionary.

    (gh-13421)

    ๐Ÿ‘‰ Use 64-bit integer size on 64-bit platforms in fallback lapack_lite

    ๐Ÿ‘‰ Use 64-bit integer size on 64-bit platforms in the fallback LAPACK
    library, which is used when the system has no LAPACK installed, allowing
    it to deal with linear algebra for large arrays.

    (gh-15218)

    ๐Ÿ‘‰ Use AVX512 intrinsic to implement np.exp when input is np.float64

    ๐Ÿ‘‰ Use AVX512 intrinsic to implement np.exp when input is np.float64,
    ๐ŸŽ which can improve the performance of np.exp with np.float64 input
    5-7x faster than before. The _multiarray_umath.so module has grown
    ๐Ÿง about 63 KB on linux64.

    (gh-15648)

    Ability to disable madvise hugepages

    ๐Ÿง On Linux NumPy has previously added support for madavise hugepages which
    ๐ŸŽ can improve performance for very large arrays. Unfortunately, on older
    0๏ธโƒฃ Kernel versions this led to peformance regressions, thus by default the
    ๐Ÿ‘Œ support has been disabled on kernels before version 4.6. To override the
    0๏ธโƒฃ default, you can use the environment variable:

    NUMPY_MADVISE_HUGEPAGE=0
    

    ๐Ÿ‘ or set it to 1 to force enabling support. Note that this only makes a
    difference if the operating system is set up to use madvise transparent
    hugepage.

    (gh-15769)

    numpy.einsum accepts NumPy int64 type in subscript list

    There is no longer a type error thrown when numpy.einsum is passed a
    NumPy int64 array as its subscript list.

    (gh-16080)

    np.logaddexp2.identity changed to -inf

    The ufunc ~numpy.logaddexp2 now has an identity of -inf, allowing it
    to be called on empty sequences. This matches the identity of
    ~numpy.logaddexp.

    (gh-16102)

    ๐Ÿ”„ Changes

    Remove handling of extra argument to __array__

    โœ… A code path and test have been in the code since NumPy 0.4 for a
    two-argument variant of __array__ (dtype=None, context=None). It was
    activated when calling ufunc(op) or ufunc.reduce(op) if
    op. __array__ existed. However that variant is not documented, and it
    ๐Ÿšš is not clear what the intention was for its use. It has been removed.

    (gh-15118)

    numpy.random._bit_generator moved to numpy.random.bit_generator

    In order to expose numpy.random.BitGenerator and
    ๐Ÿ‘€ numpy.random.SeedSequence to Cython, the _bitgenerator module is now
    public as numpy.random.bit_generator

    Cython access to the random distributions is provided via a pxd file

    c_distributions.pxd provides access to the c functions behind many of
    the random distributions from Cython, making it convenient to use and
    extend them.

    (gh-15463)

    ๐Ÿ›  Fixed eigh and cholesky methods in numpy.random.multivariate_normal

    Previously, when passing method='eigh' or method='cholesky',
    numpy.random.multivariate_normal produced samples from the wrong
    ๐Ÿ›  distribution. This is now fixed.

    (gh-15872)

    ๐Ÿ›  Fixed the jumping implementation in MT19937.jumped

    This fix changes the stream produced from jumped MT19937 generators. It
    does not affect the stream produced using RandomState or MT19937
    ๐Ÿ‘€ that are directly seeded.

    ๐ŸŒ The translation of the jumping code for the MT19937 contained a reversed
    loop ordering. MT19937.jumped matches the Makoto Matsumoto's original
    implementation of the Horner and Sliding Window jump methods.

    (gh-16153)

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