Make the FANTOIR code more pythonic

Summary:
Scripts with functions should allow to be included in other source files.

Apply more pythonic style. Ask forgiveness not permission.

Test Plan:
Check if the behavior is unchanged.

./extract_streets.py FANTOIR1017 before.txt

git pull

./extract_streets.py FANTOIR1017 after.txt

diff before.txt after.txt

Reviewers: dereckson

Reviewed By: dereckson

Differential Revision: https://devcentral.nasqueron.org/D1230