Session03

Created branch session03 and added script list_lab.py
@cewing It does look odd and is not the PEP 8 recommended way to include comments, but I believe it is ignored by the interpreter. From PEP 257:

>String literals occurring elsewhere in Python code may also act as documentation. They are not recognized by the Python bytecode compiler and are not accessible as runtime object attributes... 

[Also, in a tweet from Guido](https://mobile.twitter.com/gvanrossum/status/112670605505077248)