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class PropertyCache:
"""Mixin class providing a simple cache."""
def __init__(self):
self._cache = {}
def _try_cache(self, cache_key, cache_populate_func):
"""Tries to get a value from the cache identified by `cache_key`.
If no value is found in the cache, do a function call to `cache_populate_func` to populate the cache
and then return the value from the cache."""
if cache_key not in self._cache:
cache_populate_func()
return self._cache[cache_key]
def cache(original_func=None, cachekey=None):
"""Cache decorator. Caches function return values.
Requires the parent class to extend and initialize PropertyCache.
Usage:
# Use function name as cache key
@cache
def myfunc(args):
...
# Specify cache key
@cache(cachekey="foobar")
def myfunc(args):
...
"""
# Decorators with optional arguments are a bit convoluted in python, see some of the links below for details.
def cache_decorator(func):
# Use 'nonlocal' keyword to access parent function variable:
# https://stackoverflow.com/a/14678445/381010
nonlocal cachekey
if not cachekey:
cachekey = func.__name__
def wrapped(*args):
def cache_func_result():
# Call decorated function and store its result in the cache
args[0]._cache[cachekey] = func(*args)
return args[0]._try_cache(cachekey, cache_func_result)
return wrapped
# To support optional kwargs for decorators, we need to check if a function is passed as first argument or not.
# https://stackoverflow.com/a/24617244/381010
if original_func:
return cache_decorator(original_func)
return cache_decorator
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