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ENH: Additions to np.farray API #14966

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5 changes: 5 additions & 0 deletions doc/release/upcoming_changes/14966.new_feature.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
`numpy.asfarray` accepts `copy` argument
----------------------------------------
It is now possible to force `asfarray` to make a copy using `copy=True`.
`dtype` also accepts an argument of `None`, to attempt to preserve the type of
any array-like.
45 changes: 40 additions & 5 deletions numpy/lib/tests/test_type_check.py
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Expand Up @@ -469,14 +469,49 @@ def test_basic(self):
assert_all(isrealobj(b))


class TestArrayConversion(object):
class TestAsfarray(object):

def test_asfarray(self):
a = asfarray(np.array([1, 2, 3]))
def test_basic(self):
a = asfarray([1, 2, 3])
assert_equal(a.__class__, np.ndarray)
assert_(np.issubdtype(a.dtype, np.floating))

b = asfarray(np.array([1, 2, 3]))
assert_equal(b.__class__, np.ndarray)
assert_(np.issubdtype(b.dtype, np.floating))

def test_dtype(self):
a = asfarray(np.array([1, 2, 3]), dtype=np.int32)
assert_(np.issubdtype(a.dtype, np.floating))

a = asfarray(np.array([1, 2, 3]), dtype=np.float16)
assert_(np.issubdtype(a.dtype, np.floating))

a = asfarray(np.array([1, 2, 3]), dtype=np.complex128)
assert_(np.issubdtype(a.dtype, np.complexfloating))

def test_dtype_none(self):
a = asfarray(np.array([1, 2, 3]), dtype=None)
assert_(np.issubdtype(a.dtype, np.floating))

b = asfarray(np.array([1.0, 2.0, 3.0]), dtype=None)
assert_(np.issubdtype(b.dtype, np.inexact))

c = asfarray(np.array([1.0+1j, 2.0+2j, 3.0+3j]), dtype=None)
assert_(np.issubdtype(c.dtype, np.complexfloating))

def test_dtype_array(self):
# previously this would infer dtypes from arrays, unlike every single
# other numpy function
assert_raises(TypeError,
asfarray, np.array([1, 2, 3]), dtype=np.array(1.0))
assert_raises(TypeError, asfarray,
np.array([1, 2, 3]), dtype=np.array(1.0))

def test_copy(self):
a = np.array([1, 2, 3])
assert_(asfarray(a, copy=False) is not a)
assert_(asfarray(a, copy=True) is not a)

b = np.array([1.0, 2.0, 3.0])
assert_(asfarray(b, copy=False) is b)
assert_(asfarray(b, copy=True) is not b)

23 changes: 18 additions & 5 deletions numpy/lib/type_check.py
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Expand Up @@ -10,6 +10,7 @@
'typename', 'asfarray', 'mintypecode', 'asscalar',
'common_type']

from numpy.core.multiarray import array
import numpy.core.numeric as _nx
from numpy.core.numeric import asarray, asanyarray, isnan, zeros
from numpy.core.overrides import set_module
Expand Down Expand Up @@ -80,22 +81,26 @@ def mintypecode(typechars, typeset='GDFgdf', default='d'):
return l[0][1]


def _asfarray_dispatcher(a, dtype=None):
def _asfarray_dispatcher(a, dtype=None, copy=None):
return (a,)


@array_function_dispatch(_asfarray_dispatcher)
def asfarray(a, dtype=_nx.float_):
def asfarray(a, dtype=_nx.float_, copy=False):
"""
Return an array converted to a float type.

Parameters
----------
a : array_like
The input array.
dtype : str or dtype object, optional
dtype : str or dtype object or None, optional
Float type code to coerce input array `a`. If `dtype` is one of the
'int' dtypes, it is replaced with float64.
'int' dtypes, it is replaced with float64. If `None`, use the dtype of
the array itself in the same way.
copy : bool
If `True`, a copy will be returned even if the input array meets the
type criteria.

Returns
-------
Expand All @@ -112,9 +117,17 @@ def asfarray(a, dtype=_nx.float_):
array([2., 3.])

"""
if dtype is None:
orig = a
a = array(orig, copy=False, subok=False, order=None)
dtype = a.dtype
if a is not orig:
copy = False

if not _nx.issubdtype(dtype, _nx.inexact):
dtype = _nx.float_
return asarray(a, dtype=dtype)

return array(a, dtype=dtype, copy=copy, subok=False, order=None)


def _real_dispatcher(val):
Expand Down