diff --git a/09_dynamic_programming/python/01_longest_common_subsequence.py b/09_dynamic_programming/python/01_longest_common_subsequence.py
new file mode 100644
index 0000000..9f74f93
--- /dev/null
+++ b/09_dynamic_programming/python/01_longest_common_subsequence.py
@@ -0,0 +1,6 @@
+if word_a[i] == word_b[j]:
+  # The letters match.
+  cell[i][j] = cell[i-1][j-1] + 1
+else:
+  # The letters don't match.
+  cell[i][j] = max(cell[i-1][j], cell[i][j-1])