Advancted functions

1. Variable scopes
2. Name resolution order (LEGB)
3. Scoping: global seen from fuction
4. Assignment creates local scope
5. Local scope gone wrong
6. Changing global variable from a function
7. Global variables mutable in functions
8. Scoping issues
9. sub in sub
10. Scoping sub in sub (enclosing scope)
11. Function objects
12. Functions are created at run time
13. Mutable default
14. Use None as default parameter
15. Inner function created every time the outer function runs
16. Static variable
17. Static variable in generated function
18. Inspect