python matrix added.

EXERCISES.txt

@@ -1,5 +1,6 @@
 bob
 rna-transcription
+matrix
 word-count
 anagram
 beer-song

matrix/example.py

@@ -0,0 +1,8 @@
+class Matrix(object):
+    def __init__(self, s):
+        self.rows = [[int(n) for n in row.split()]
+                     for row in s.split('\n')]
+
+    @property
+    def columns(self):
+        return map(list, zip(*self.rows))

matrix/matrix_test.py

@@ -0,0 +1,36 @@
+try:
+    from matrix import Matrix
+except ImportError:
+    raise SystemExit('Could not find matrix.py. Does it exist?')
+
+import unittest
+
+
+class MatrixTest(unittest.TestCase):
+    def test_extract_a_row(self):
+        matrix = Matrix("1 2\n10 20")
+        self.assertEqual([1, 2], matrix.rows[0])
+
+    def test_extract_same_row_again(self):
+        matrix = Matrix("9 7\n8 6")
+        self.assertEqual([9, 7], matrix.rows[0])
+
+    def test_extract_other_row(self):
+        matrix = Matrix("9 8 7\n19 18 17")
+        self.assertEqual([19, 18, 17], matrix.rows[1])
+
+    def test_extract_other_row_again(self):
+        matrix = Matrix("1 4 9\n16 25 36")
+        self.assertEqual([16, 25, 36], matrix.rows[1])
+
+    def test_extract_a_column(self):
+        matrix = Matrix("1 2 3\n4 5 6\n7 8 9\n 8 7 6")
+        self.assertEqual([1, 4, 7, 8], matrix.columns[0])
+
+    def test_extract_another_column(self):
+        matrix = Matrix("89 1903 3\n18 3 1\n9 4 800")
+        self.assertEqual([1903, 3, 4], matrix.columns[1])
+
+
+if __name__ == '__main__':
+    unittest.main()