Second part of the Python Master class covering advanced topics and sqlalchemy.

1. Python Master Class
Part 2
By Chathuranga Bandara
www.chathuranga.com

2. Agenda
Some advanced concepts in Python
Exceptions Handling in Python
ORM - SQLAlchemy
Unit testing in Python

3. Generators
Generators are a simple and powerful tool for creating iterators.

4. ie:

5. What is wrong there?
The code is quite simple and straightforward, but its builds the full list in memory. This is clearly not acceptable in our case,
because we cannot afford to keep all n "10 megabyte" integers in memory.

6. Generator pattern may be?

7. Still Have issues.
● Lots of code / boilerplate
● Hard to read

8. Generators to the Rescue!

9. Some Dark Magic there! WTF is yield?

10. Yield is a keyword that is used like return, except the function will return a
generator.

11. When a yield statement is executed, the state of the generator is frozen and the
value of expression_list is returned to next()‘s caller. By “frozen” we mean that all
local state is retained, including the current bindings of local variables, the
instruction pointer, and the internal evaluation stack: enough information is saved
so that the next time next() is invoked, the function can proceed exactly as if the
yield statement were just another external call.

12. Iterators
It's a stateful helper object that will produce the next value when you call next() on
it. Any object that has a __next__() method is therefore an iterator. How it
produces a value is irrelevant.

13. ie: inbuilt iterators

15. Custom Iterators

16. Decorators
Some sh*t which is very useful

17. What is a decorator?
decorators dynamically alter the functionality of a function, method or class without
having to directly use subclasses.

18. Some Context
We can assign names to functions right?

19. Also Closures. (yes. JS stole it from here)

20. Also Higher Order Functions

21. Return a function

23. Finally Decorators! (stitch all the sh*t together)

24. Python Decorator Syntax

27. Better way?

28. Passing Arguments to decorators

29. More Pythonic

30. Exceptions Handling in Python
Try and Catch that nigga!

31. Syntax

33. How to raise an Exception

34. Custom Exceptions

35. ORM for Flask

36. pip install Flask-SQLAlchemy

41. Relationships?

44. Do Something!

45. Small Applications
/yourapplication
/yourapplication.py
/static
/style.css
/templates
layout.html
index.html
login.html
...

46. Packages
/yourapplication
/runserver.py
/yourapplication
/__init__.py
/views.py
/static
/style.css
/templates
layout.html
index.html
login.html
...

47. With Blueprints
yourapp/
__init__.py
static/
templates/
home/
control_panel/
admin/
views/
__init__.py
home.py
control_panel.py
admin.py
models.py

50. Unit Testing

51. Inbuilt?

53. Nose helps you manage unit tests

55. pip install unittest2

57. Questions?

58. That’s all for today Folks!