Update free-programming-books.md

I added some more Free Python sources and a link to PDF file.

free-programming-books.md

@@ -782,6 +782,7 @@ See also [TeX](#tex)
 * [Data Structures and Algorithms in Python](http://www.brpreiss.com/books/opus7/html/book.html)
 * [Dive into Python](http://www.diveintopython.net/)
 * [Dive into Python 3](http://getpython3.com/diveintopython3/)
+* [Google's Python Class](https://developers.google.com/edu/python/?hl=de-DE&csw=1)
 * [Hacking Secret Cyphers with Python](http://inventwithpython.com/hacking/chapters/) - Al Sweigart
 * [Hitchiker's Guide to Python!](http://docs.python-guide.org/en/latest/)
 * [How to Think Like a Computer Scientist: Learning with Python](http://www.greenteapress.com/thinkpython/thinkCSpy/)
@@ -796,6 +797,8 @@ See also [TeX](#tex)
 * [Python for Fun](http://www.openbookproject.net/py4fun/)
 * [Python for Informatics: Exploring Information](http://www.pythonlearn.com/book.php)
 * [Python for you and me](http://pymbook.readthedocs.org/en/latest/)
+* [Python Practice Book](http://anandology.com/python-practice-book/index.html)
+* [Python Programming](http://upload.wikimedia.org/wikipedia/commons/9/91/Python_Programming.pdf) - PDF
 * [Python Scientific Lecture Notes](http://scipy-lectures.github.io/)
 * [Snake Wrangling For Kids](http://www.briggs.net.nz/snake-wrangling-for-kids.html)
 * [Think Python](http://www.greenteapress.com/thinkpython/) - Allen B. Downey