Update; add headers to py files

.commit_template

@@ -1,5 +1,20 @@
-# Title. No more than 50 characters        ----> |
 
-# Leave a single blank line between the title and the body (excluding comments)
 
-# Body. Write a description of what you've changed. 
+# -----------------------------------------------------------------
+# Write your entire commit message above this line.
+# 
+# The first line should be a quick description of what you changed.
+# Then leave a blank line. 
+# Then, taking as many lines as you want, answer the questions for 
+# your current checkpoint: 
+#
+# Checkpoint 1: You are starting to work with more complex data structures.
+# Reflect on one place you got stuck--because you weren't sure
+# what you needed the program to do, because you weren't sure how to 
+# use the new syntax, or for another reason. What strategies did you use
+# to get un-stuck?
+#
+# Checkpoint 2: Sections 2.1, 2.2, and 2.3 talk about computer systems 
+# at three different scales: functions (within a Python program), 
+# programs (running in Terminal), and distributed services (running
+# across the Internet). Explain what these systems have in common.