MAINT: special_matrices: add a note about handling of empty sequences

Also pep8-ify the test.
belltailjp · Apr 4, 2015 · d2537fa · d2537fa
1 parent 4739653
commit d2537fa
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Showing 2 changed files with 11 additions and 3 deletions.
diff --git a/scipy/linalg/special_matrices.py b/scipy/linalg/special_matrices.py
@@ -484,7 +484,7 @@ def block_diag(*arrs):
     Parameters
     ----------
     A, B, C, ... : array_like, up to 2-D
-        Input arrays.  A 1-D array or array_like sequence of length `n`is
+        Input arrays.  A 1-D array or array_like sequence of length `n` is
         treated as a 2-D array with shape ``(1,n)``.
 
     Returns
@@ -498,6 +498,8 @@ def block_diag(*arrs):
     If all the input arrays are square, the output is known as a
     block diagonal matrix.
 
+    Empty sequences (i.e., array-likes of zero size) are ignored.
+
     Examples
     --------
     >>> from scipy.linalg import block_diag

diff --git a/scipy/linalg/tests/test_special_matrices.py b/scipy/linalg/tests/test_special_matrices.py
@@ -262,8 +262,14 @@ def test_no_args(self):
 
     def test_empty_matrix_arg(self):
         # regression test for gh-4596: check the shape of the result for empty matrix inputs
-        a = block_diag([[1, 0], [0, 1]], [], [[2, 3], [4, 5], [6, 7]])
-        assert_array_equal(a, [[1, 0, 0, 0], [0, 1, 0, 0], [0, 0, 2, 3], [0, 0, 4, 5], [0, 0, 6, 7]])
+        a = block_diag([[1, 0], [0, 1]],
+                       [],
+                       [[2, 3], [4, 5], [6, 7]])
+        assert_array_equal(a, [[1, 0, 0, 0],
+                               [0, 1, 0, 0],
+                               [0, 0, 2, 3],
+                               [0, 0, 4, 5],
+                               [0, 0, 6, 7]])
 
 
 class TestKron: