Merge branch 'add-reshaped-view' into 'master'

Add reshaped_view function

See merge request !13

pytools/__init__.py

@@ -129,6 +129,12 @@ Functions for dealing with (large) auxiliary files
 --------------------------------------------------
 
 .. autofunction:: download_from_web_if_not_present
+
+Helpers for :mod:`numpy`
+------------------------
+
+.. autofunction:: reshaped_view
+
 """
 
 
@@ -2033,6 +2039,26 @@ def find_module_git_revision(module_file, n_levels_up):
 # }}}
 
 
+# {{{ create a reshaped view of a numpy array
+
+def reshaped_view(a, newshape):
+    """ Create a new view object with shape ``newshape`` without copying the data of
+    ``a``. This function is different from ``numpy.reshape`` by raising an
+    exception when data copy is necessary.
+
+    :arg a: a :class:`numpy.ndarray` object.
+    :arg newshape: an ``int`` object or a tuple of ``int`` objects.
+
+    .. versionadded:: 2018.4
+    """
+
+    newview = a.view()
+    newview.shape = newshape
+    return newview
+
+# }}}
+
+
 def _test():
     import doctest
     doctest.testmod()

test/test_pytools.py

@@ -211,6 +211,18 @@ def test_find_module_git_revision():
     print(pytools.find_module_git_revision(pytools.__file__, n_levels_up=1))
 
 
+def test_reshaped_view():
+    import pytools
+    import numpy as np
+
+    a = np.zeros((10, 2))
+    b = a.T
+    c = pytools.reshaped_view(a, -1)
+    assert c.shape == (20,)
+    with pytest.raises(AttributeError):
+        pytools.reshaped_view(b, -1)
+
+
 if __name__ == "__main__":
     if len(sys.argv) > 1:
         exec(sys.argv[1])