The Scientist & The Engineer

My keynote from PyCon Colombia 2020.

Transcript

1. THE SCIENTIST
   ANDREW GODWIN // @andrewgodwin
   THE ENGINEER
   AND
   

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2. Hi, I’m
   Andrew Godwin
   

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3. I call myself an "engineer"
   

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4. But I studied Computer Science
   

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5. I knew programming going in.
   But this was different.
   

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6. “
   Edsger Dijkstra
   Computer science is no
   more about computers
   than astronomy is about
   telescopes.
   

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7. Computer Science is idealistic
   

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8. "Turing-complete"
   

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9. We first want to prove it is possible
   

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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
    

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11. We can prove that programs are correct
    

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12. def is_two(number):
    return number == 2
    

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13. >>> import __builtin__
    >>> __builtin__.True = False
    >>> True
    False
    >>> True == False
    True
    (Thankfully, only works in Python 2!)
    

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14. "Communicating Sequential Processes", C. A. R Hoare
    

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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
    

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16. A perfect world, of perfect programs
    

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17. “
    Benjamin Brewster
    In theory there is no
    difference between
    theory and practice.
    In practice there is.
    

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18. Software Engineering takes shortcuts
    

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19. When is it safe to take a risk?
    

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21. Software is faster and cheaper to change
    

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22. The real world is a nasty place
    

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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!
    

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24. Always design for failure
    

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25. How do we reason about software?
    

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26. Input
    Process
    Output
    

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27. async def disable_alarm():
    ...
    async def open_door():
    ...
    await asyncio.wait(
    [disable_alarm(), open_door()]
    )
    

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28. Input
    Rendering
    Output
    Validation
    Reporting
    Storage
    Processing
    Logging
    Cache
    

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29. Django has 250,000 lines of code
    

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30. An Airbus A380 has 4,000,000 parts
    

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31. A new car has 100,000,000 lines of code
    

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32. How are we supposed to handle this?
    

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33. Abstract, verify and forget
    

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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
    

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35. You have to learn to forget
    

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36. Engineering is communication
    

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37. “
    Grace Hopper
    A ship in port is safe, but that's not
    what ships are built for.
    

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38. Build to expect growth
    

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39. Build to expect failure
    

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40. Everyone can build near-perfect software
    

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41. Know when not to!
    

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42. Python lets you do both.
    

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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.
    

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44. Scientists observe and question
    

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45. Engineers build and invent
    

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46. All software has consequences
    

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47. Be the scientist and the engineer
    

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48. Gracias.
    Andrew Godwin
    @andrewgodwin // aeracode.org
    

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