caching in python

py-cache/cache.py

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+from functools import wraps
+
+
+def cached(fn):
+ cache = {} # args -> value
+
+ @wraps(fn)
+ def wrapper(*args, **kw):
+ if args in cache:
+ return cache[args]
+
+ value = cache[args] = fn(*args)
+ return value
+
+ return wrapper

py-cache/caching.md

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+# Caching
+
+Save a computation result and using it later. AKA memoization.
+
+You trade memory consumption for performance.
+
+Works on "pure" functions that don't have side effects.

py-cache/current.txt

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+13

py-cache/end.ipy

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+import os
+
+!kitty +icat book-covers.png
+width = os.get_terminal_size().columns
+url = 'https://pragprog.com/search/?q=miki+tebeka'
+print(f'{url:^{width}}')

py-cache/four.md

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+There's two hard problems in computer science: We only have one joke and it's not funny.
+
+- Phillip Scott Bowden

py-cache/header.md

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+# Caching in Python
+[Miki Tebeka](mailto:[email protected])
+

py-cache/libs.md

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+# Use Libraries
+
+
+The "Not Invented Here" (NIH) Syndrome is the tendency to reject ideas that come from "outside". 
+And unfortunately, "outside" can still apply to solutions that come from other teams within the organization.
+
+- functools.lru_cache
+ - https://docs.python.org/3/library/functools.html#functools.lru_cache
+- joblib.Memory
+ - https://joblib.readthedocs.io/en/latest/memory.html#memory
+- Redis/Memcached
+ - https://redis.io/
+ - https://memcached.org/
+

py-cache/next.ipy

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+current = 'current.txt'
+
+try:
+ with open(current) as fp:
+ i = int(fp.read())
+except OSError:
+ i = 0
+
+!clear
+if i == 0:
+ !glow caching.md
+elif i == 1:
+ !source-highlight -n -f esc -s python -i user.py
+ %run user.py
+elif i == 2:
+ !source-highlight -n -f esc -s python -i cache.py
+elif i == 3:
+ !source-highlight -n -f esc -s python -i user_cached.py
+ %run user_cached.py
+elif i == 4:
+ !glow two.md
+elif i == 5:
+ !glow three.md
+elif i == 6:
+ !glow four.md
+elif i == 7:
+ !glow libs.md
+elif i == 8:
+ !source-highlight -n -f esc -s python -i user_lru.py
+ %run user_lru.py
+elif i == 9:
+ !source-highlight -n -f esc -s python -i user_mem.py
+ %run user_mem.py
+else:
+ echo 'Thank You!' | cowsay | lolcat -a -d 3
+
+
+with open(current, 'w') as out:
+ print(i+1, file=out, end='')

py-cache/playbook.md

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+%run setup.py
+
+%timeit get_user('bruce')
+
+In cache show get_user(['bruce'])

py-cache/setup.ipy

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+%alias_magic -p next.ipy next %run
+%alias_magic -p end.ipy end %run
+!rm -f current.txt
+!clear
+!glow header.md

py-cache/three.md

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+There are 2 hard problems in computer science: cache invalidation, naming things, and off-by-1 errors.
+
+- Leon Bambrick

py-cache/two.md

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+There are only two hard things in Computer Science: cache invalidation and naming things.
+
+- Phil Karlton

py-cache/user.py

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+from dataclasses import dataclass
+from time import sleep
+
+@dataclass
+class User:
+ login: str
+ name: str
+ roles: list[str]
+
+
+def get_user(login):
+ sleep(0.1) # simulate DB access
+ return User(login, 'Bruce', ['ADMIN'])
+

py-cache/user_cached.py

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+from dataclasses import dataclass
+from time import sleep
+
+from cache import cached
+
+@dataclass
+class User:
+ login: str
+ name: str
+ roles: list[str]
+
+
+@cached
+def get_user(login):
+ sleep(0.1) # simulate DB access
+ return User(login, 'Bruce', ['ADMIN'])
+

py-cache/user_lru.py

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+from dataclasses import dataclass
+from time import sleep
+
+from functools import lru_cache
+
+@dataclass
+class User:
+ login: str
+ name: str
+ roles: list[str]
+
+
+@lru_cache(1024)
+def get_user(login):
+ sleep(0.1) # simulate DB access
+ return User(login, 'Bruce', ['ADMIN'])
+

py-cache/user_mem.py

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+from dataclasses import dataclass
+from time import sleep
+
+from joblib import Memory
+
+memory = Memory('/tmp/users', verbose=False)
+
+@dataclass
+class User:
+ login: str
+ name: str
+ roles: list[str]
+
+
+@memory.cache
+def get_user(login):
+ sleep(0.1) # simulate DB access
+ return User(login, 'Bruce', ['ADMIN'])
+