NF: add utils module for code support functions

Add to_scalar function with tests.

Author: matthew-brett

nibabel/tests/test_utils.py

@@ -0,0 +1,22 @@
+""" Test for utils module
+"""
+
+import numpy as np
+
+from nibabel.utils import to_scalar
+
+from nose.tools import assert_equal, assert_true, assert_false, assert_raises
+
+
+def test_to_scalar():
+    for pass_thru in (2, 2.3, 'foo', b'foo', [], (), [2], (2,), object()):
+        assert_true(to_scalar(pass_thru) is pass_thru)
+    for arr_contents in (2, 2.3, 'foo', b'foo'):
+        arr = np.array(arr_contents)
+        out = to_scalar(arr)
+        assert_false(to_scalar(arr) is arr)
+        assert_equal(out, arr_contents)
+        # Promote to 1 and 2D and check contents
+        assert_equal(to_scalar(np.atleast_1d(arr)), arr_contents)
+        assert_equal(to_scalar(np.atleast_2d(arr)), arr_contents)
+    assert_raises(ValueError, to_scalar, np.array([1, 2]))

nibabel/utils.py

@@ -0,0 +1,21 @@
+""" Code support routines, not otherwise classified
+"""
+
+
+def to_scalar(val):
+    """ Return scalar representation of `val`
+
+    Return scalar value from numpy array, or pass through value if not numpy
+    array.
+
+    Parameters
+    ----------
+    val : object
+        numpy array or other object.
+
+    Returns
+    -------
+    out : object
+        Result of ``val.item()`` if `val` has an ``item`` method, else `val`.
+    """
+    return val.item() if hasattr(val, 'item') else val