The Scientist & The Engineer

My keynote from PyCon Colombia 2020.

1. THE SCIENTIST ANDREW GODWIN // @andrewgodwin THE ENGINEER AND
2. Hi, I’m Andrew Godwin
3. I call myself an "engineer"
4. But I studied Computer Science
5. I knew programming going in. But this was different.
6. “ Edsger Dijkstra Computer science is no more about computers than astronomy is about telescopes.
7. Computer Science is idealistic
8. "Turing-complete"
9. We first want to prove it is possible
10. async def sleep_sort(numbers): async def sleep_add(number): await asyncio.sleep(number) result.append(number) result = [] await asyncio.wait([ sleep_add(number) for number in numbers ]) return result
11. We can prove that programs are correct
12. def is_two(number): return number == 2
13. >>> import __builtin__ >>> __builtin__.True = False >>> True False >>> True == False True (Thankfully, only works in Python 2!)
14. "Communicating Sequential Processes", C. A. R Hoare
15. contains :: (Ord a) => (Tree a) -> a -> Bool contains Nil _ = False contains (Node t1 v t2) x | x == v = True | x < v = contains t1 x | x > v = contains t2 x
16. A perfect world, of perfect programs
17. “ Benjamin Brewster In theory there is no difference between theory and practice. In practice there is.
18. Software Engineering takes shortcuts
19. When is it safe to take a risk?
21. Software is faster and cheaper to change
22. The real world is a nasty place
23. How often does a cosmic ray affect RAM? 36 hours (for 16GB; "SEU at Ground Level", Eugene Normand) How long can an unpowered SSD keep data? 3 weeks - 1 year (Enterprise at 40ºC, Client at 30ºC; Intel/JEDEC) Does quantum tunneling affect CPUs? Continuously!
24. Always design for failure
25. How do we reason about software?
26. Input Process Output
27. async def disable_alarm(): ... async def open_door(): ... await asyncio.wait( [disable_alarm(), open_door()] )
28. Input Rendering Output Validation Reporting Storage Processing Logging Cache
29. Django has 250,000 lines of code
30. An Airbus A380 has 4,000,000 parts
31. A new car has 100,000,000 lines of code
32. How are we supposed to handle this?
33. Abstract, verify and forget
34. Abstract Define a contract - types, behaviour, exceptions Verify Write tests to keep the contract valid Forget Work with the contract, not the fine details
35. You have to learn to forget
36. Engineering is communication
37. “ Grace Hopper A ship in port is safe, but that's not what ships are built for.
38. Build to expect growth
39. Build to expect failure
40. Everyone can build near-perfect software
41. Know when not to!
42. Python lets you do both.
43. Types Start without types, progressively add with mypy Async Make it work synchronously first. Add async later. Speed Write slow, understandable code. Test it. Then improve it.
44. Scientists observe and question
45. Engineers build and invent
46. All software has consequences
47. Be the scientist and the engineer
48. Gracias. Andrew Godwin @andrewgodwin // aeracode.org