Snake Snacks: Function Composition, The Dumb Way

Transcript

1. Snake Snacks FUNCTION COMPOSITION, THE DUMB WAY
2. WHAT WE WANT def inc(n): return n + 1 def double(n): return n * 2 # in the REPL >>> (inc >> double)(2) 6 >>> (double >> inc)(2) 5
3. HOW ARE WE GONNA GET THERE? The Worst Way Possible™
4. DOUBLE UNDERSCORE METHODS
5. DOUBLE UNDERSCORE METHODS
6. DUNDER METHODS
7. DUNDER MIFFLIN
8. DUNDER METHODS, THE NICE WAY class Boss(object): def __init__(self, name): self.name = name def __str__(self): return self.name def __repr__(self): return '<%s: %s>' % (self.__class__.__name__, self) def introduce(self): return "Please meet my boss, %s" % self
9. DUNDER METHODS, THE NICE WAY >>> b = Boss("Michael Scott") >>> b <Boss: Michael Scott> >>> str(b) 'Michael Scott' >>> b.introduce() 'Please meet my boss, Michael Scott'
10. ! DECORATORS "
11. DECORATORS, THE NICE WAY def memoize(fn): cache = {} def inner(*args, **kwargs): key = str((args, kwargs)) if key not in cache: cache[key] = fn(*args, **kwargs) return cache[key] return inner
12. DECORATORS, THE NICE WAY @memoize def hype(stuff): return "OH YEAH, IT'S %s" % stuff.upper() # is the same as... hype = memoize(lambda stuff: "OH YEAH, IT'S %s" % stuff.upper())
13. DECORATORS, THE NICE WAY >>> hype("cheese") "OH YEAH, IT'S CHEESE" >>> hype("a moose") "OH YEAH, IT'S A MOOSE"
14. BUT… OBJECTS! class memoize(object): def __init__(self, fn): self.cache = {} self.fn = fn def __call__(self, *args, **kwargs): key = str((args, kwargs)) if key not in self.cache: self.cache[key] = self.fn(*args, **kwargs) return self.cache[key]
15. BUT… OBJECTS! >>> hype("cheese") "OH YEAH, IT'S CHEESE" >>> hype("a moose") "OH YEAH, IT'S A MOOSE" >>> hype.cache {"(('a moose',), {})": "OH YEAH, IT'S A MOOSE", "(('cheese',), {})": "OH YEAH, IT'S CHEESE"}
16. __gt__ class ChessPlayer(object): def __init__(self, name, elo): self.name = name self.elo = elo def __gt__(self, other): return self.elo > other.elo
17. __gt__ >>> carlsen = ChessPlayer("Carlsen, Magnus", 2827) >>> almasi = ChessPlayer("Almasi, Zoltan", 2707) >>> carlsen > almasi True >>> carlsen < almasi False
18. OUR FIRST TRY! class composable(object): def __init__(self, fn): self.fn = fn def __call__(self, *args, **kwargs): return self.fn(*args, **kwargs) def __gt__(self, other): return self.__class__( lambda *args, **kwargs: other(self.fn(*args, **kwargs)) )
19. OUR FIRST TRY! @composable def inc(n): return n + 1 @composable def double(n): return n * 2 @composable def triple(n): return n * 3
20. OUR FIRST TRY! >>> (inc > inc)(0) 2 >>> (inc > inc > inc)(0) 2
21. OUR FIRST TRY! ! 1 > 2 > 3 # is equivalent to 1 > 2 and 2 > 3 # NOT (1 > 2) > 3
22. __rshift__ TO THE RESCUE! class composable(object): def __init__(self, fn): self.fn = fn def __call__(self, *args, **kwargs): return self.fn(*args, **kwargs) def __rshift__(self, other): return self.__class__( lambda *args, **kwargs: other(self.fn(*args, **kwargs)) )
23. __rshift__ TO THE RESCUE! >>> (inc >> inc)(0) 2 >>> (inc >> inc >> inc)(0) 3
24. __rshift__ TO THE RESCUE! >>> (inc >> double)(2) 6 >>> (double >> inc)(2) 5 >>> (inc >> double >> triple)(2) 18
25. THANK YOU I'M SORRY