# HG changeset patch
# User Jeff Hammel <k0scist@gmail.com>
# Date 1513544027 28800
# Node ID 4bf2145c16f8f3f555e98a748d32967e6ba39c15
# Parent  9f1324a59cc1641b1bc3414735198549776787c3
and quick transposition function

diff -r 9f1324a59cc1 -r 4bf2145c16f8 tvii/transpose.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tvii/transpose.py	Sun Dec 17 12:53:47 2017 -0800
@@ -0,0 +1,28 @@
+from .unique import unique
+from .unique import NotUnique
+
+
+class NotAMatrix(Exception):
+    """marker exception for matrix conformity"""
+
+
+def transpose(A):
+    """transpose a 2D matrix, `A`"""
+
+    if not A:
+        # empty matrix
+        return A
+
+    # Asset that all rows have the same length
+    try:
+        length = unique([len(row) for row in A])
+    except NotUnique as e:
+        raise NotAMatrix("Multiple number of columns detected: {}".format(sorted(e.multiples)))
+
+    # perform the transpose
+    transposed = [[None for i in range(len(A))]
+                  for j in range(length)]
+    for i, row in enumerate(A):
+        for j, col in enumerate(row):
+            transposed[j][i] = col
+    return transposed