BigArray: Fix API deviation with ndarray (shape)

The 'shape' argument of 'numpy.ndarray's initialization method accepts
integer and sequences of integers. But the 'shape' property of
'numpy.ndarray' always returns tuple[int, ...], so numpy manually
casts any legal argument into tuple[int, ...].

In 'BigArray' and 'ZBigArray' this internal casting didn't exist yet.
This patch adds the casting.

Before:

  ZBigArray(shape=[1, 2, 3], dtype=float).shape == [1, 2, 3]

After:

  ZBigArray(shape=[1, 2, 3], dtype=float).shape == (1, 2, 3)

In this way BigArray and ZBigArray API behaves closer to numpy.ndaray,
which should help avoiding confusion when people are using BigArray /
ZBigArray.

-----

See issue nexedi/wendelin.core#9 and
MR nexedi/wendelin.core!14
for additional context.

/reviewed-by @kirr
/reviewed-on nexedi/wendelin.core!14

bigarray/__init__.py

@@ -39,12 +39,14 @@ of physical RAM.
 from __future__ import print_function
 from wendelin.lib.calc import mul
 from wendelin.lib.xnumpy import _as_strided
+from wendelin.lib.utils import inttuple
 from numpy import ndarray, dtype, sign, newaxis, asarray, argmax, uint8
 import logging
 
 
 pagesize = 2*1024*1024 # FIXME hardcoded, TODO -> fileh.ram.pagesize
 
+
 class BigArray(object):
     # numpy.ndarray like
     # XXX can't use slots, because that would create "multiple bases have
@@ -79,6 +81,7 @@ class BigArray(object):
 
     # __init__ part without fileh
     def _init0(self, shape, dtype_, order):
+        shape = inttuple(shape)  # mimic numpy
         _dtype = dtype(dtype_)
         if _dtype.hasobject:
             logging.warn("You tried to use dtype containing object (%r) with out-of-core array ..." % _dtype)

bigarray/tests/test_basic.py

@@ -113,6 +113,22 @@ def test_bigarray_noobject(testbig):
             BigArray((1,), dtype_, Zh)
 
 
+# Ensure BigArray mimics the behavior of ndarray
+# when initializing its shape property.
+# (array.shape should always return a tuple of ints,
+#  but during initialization it should allow sequences of
+#  ints or ints)
+def test_bigarray_shape_initialization(testbig):
+    def assert_shape_becomes(shape_input, shape_property):
+        assert BigArray(shape_input, float, Zh).shape == shape_property
+
+    Zh = testbig.fopen()
+
+    assert_shape_becomes([1, 4, 3], (1, 4, 3))
+    assert_shape_becomes(42, (42,))
+    assert_shape_becomes((4, 4), (4, 4))
+
+
 # basic ndarray-compatibility attributes of BigArray
 def test_bigarray_basic(testbig):
     Zh = testbig.fopen()

lib/tests/test_utils.py

+# -*- coding: utf-8 -*-
+# Wendelin.core.lib.utils | Tests
+# Copyright (C) 2022 Nexedi SA and Contributors.
+#                    Levin Zimmermann <levin.zimmermann@nexedi.com>
+#
+# This program is free software: you can Use, Study, Modify and Redistribute
+# it under the terms of the GNU General Public License version 3, or (at your
+# option) any later version, as published by the Free Software Foundation.
+#
+# You can also Link and Combine this program with other software covered by
+# the terms of any of the Free Software licenses or any of the Open Source
+# Initiative approved licenses and Convey the resulting work. Corresponding
+# source of such a combination shall include the source code for all other
+# software used.
+#
+# This program is distributed WITHOUT ANY WARRANTY; without even the implied
+# warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+#
+# See COPYING file for full licensing terms.
+# See https://www.nexedi.com/licensing for rationale and options.
+
+from fractions import Fraction
+import numpy as np
+from pytest import raises
+import six
+
+from wendelin.lib.utils import inttuple
+
+
+def test_inttuple():
+    # Test int -> tuple conversion
+    assert inttuple(1) == (1,)
+    if six.PY2:
+        assert inttuple(long(4)) == (4,)
+    
+    # Test sequence -> tuple conversion
+    assert inttuple([1, 2, 3]) == (1, 2, 3)
+    assert inttuple(np.array([1, 2, 3])) == (1, 2, 3)
+    assert inttuple((3, 2, 4)) == (3, 2, 4)
+
+    # Test exceptions
+
+    def assert_raises(object_):
+        with raises(TypeError, match="cannot be interpreted as integer"):
+            inttuple(object_)
+
+    #   No none-integer single values are allowed
+    #     non-integer numbers
+    assert_raises(3.2)
+    assert_raises(Fraction(3, 2))
+    #     other objects
+    assert_raises("privjet")
+    assert_raises({1, 2, 3})
+    assert_raises({0: 1, 1: 2})
+    #   No none-integer values inside sequences are allowed
+    assert_raises((1, 0.5))

lib/utils.py

+# -*- coding: utf-8 -*-
+# Utility functions for python part of wendelin.core
+# Copyright (C) 2022 Nexedi SA and Contributors.
+#                    Levin Zimmermann <levin.zimmermann@nexedi.com>
+#
+# This program is free software: you can Use, Study, Modify and Redistribute
+# it under the terms of the GNU General Public License version 3, or (at your
+# option) any later version, as published by the Free Software Foundation.
+#
+# You can also Link and Combine this program with other software covered by
+# the terms of any of the Free Software licenses or any of the Open Source
+# Initiative approved licenses and Convey the resulting work. Corresponding
+# source of such a combination shall include the source code for all other
+# software used.
+#
+# This program is distributed WITHOUT ANY WARRANTY; without even the implied
+# warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+#
+# See COPYING file for full licensing terms.
+# See https://www.nexedi.com/licensing for rationale and options.
+
+import numpy as np
+import numbers
+import six
+
+if six.PY2:
+  from collections import Sequence
+else:
+  from collections.abc import Sequence
+
+
+def inttuple(int_or_int_sequence):
+    # Imitate the behaviour of numpy by converting
+    # int or sequence of int to a tuple of int and
+    # raise error in case this is not possible.
+
+    # See the following numpy + cpython references:
+    #
+    #   https://github.com/numpy/numpy/blob/28e9227565b2/numpy/core/src/multiarray/conversion_utils.c#L133-L144
+    #   https://github.com/python/cpython/blob/9c4ae037b9c3/Objects/abstract.c#L1706-L1713
+
+    def raise_if_not_integer(object_):
+        # NOTE: Use 'numbers.Integral' instead of 'int' to support
+        # python2 long type.
+        if not isinstance(object_, numbers.Integral):
+            raise TypeError(
+              "'%s' cannot be interpreted as integer" % type(object_)
+            )
+
+    # We need to explicitly add np.ndarray into checked types,
+    # because np.ndarray aren't Sequences, see also:
+    #
+    #   https://github.com/numpy/numpy/issues/2776
+    if isinstance(int_or_int_sequence, (Sequence, np.ndarray)):
+        int_tuple = tuple(int_or_int_sequence)
+        [raise_if_not_integer(object_) for object_ in int_tuple]
+        return int_tuple
+
+    raise_if_not_integer(int_or_int_sequence)
+    return (int_or_int_sequence,)