Python 中的 Cachetools 模块
原文:https://www.geeksforgeeks.org/cachetools-module-in-python/
Cachetools 是一个 Python 模块，提供各种记忆集合和装饰器。它还包括 functools 的@lru_cache 装饰器的变体。要使用它，首先，我们需要使用 pip 安装它。
pip install cachetools
Cachetools 为我们提供了五个主要功能。
- 藏起
- 乌克兰语
- TTLCache
- lrucache
- rcache
让我们通过例子详细了解以下每个函数。
藏起
缓存的用作装饰器。当我们调用 cache 时，它会缓存该函数以备后用。默认情况下，这将执行简单的缓存。
语法:
@cached(cache = {})
def some_fun():
pass
示例:我们用一个例子来看看。我们将使用时间模块来查看我们模块的效率。
from cachetools import cached
import time
# Without cached
def fib(n):
return n if n<2 else fib(n-1) + fib(n-2)
s = time.time()
print(old_fib(35))
print("Time Taken: ", time.time() - s)
# Now using cached
s = time.time()
# Use this decorator to enable caching
@cached(cache ={})
def fib(n):
return n if n<2 else fib(n-1) + fib(n-2)
print(fib(35))
print("Time Taken(cached): ", time.time() - s)
输出:
9227465
Time Taken: 4.553245782852173
9227465
Time Taken(cached): 0.0003821849822998047
乌克兰语
LRUCache 在缓存装饰器内部使用。LRU 缓存是指“最近最少使用”的缓存。它采用一个参数“maxsize”，该参数规定了应该如何缓存最近的函数。
语法:
@cached(cache= LRUCache(maxsize= 3))
def some_fun():
pass
示例:
from cachetools import cached, LRUCache
import time
# cache using LRUCache
@cached(cache = LRUCache(maxsize = 3))
def myfun(n):
# This delay resembles some task
s = time.time()
time.sleep(n)
print("\nTime Taken: ", time.time() - s)
return (f"I am executed: {n}")
# Takes 3 seconds
print(myfun(3))
# Takes no time
print(myfun(3))
# Takes 2 seconds
print(myfun(2))
# Takes 1 second
print(myfun(1))
# Takes 4 seconds
print(myfun(4))
# Takes no time
print(myfun(1))
# Takes 3 seconds because maxsize = 3
# and the 3 recent used functions had 1,
# 2 and 4.
print(myfun(3))
输出:
Time Taken: 3.0030977725982666
I am executed: 3
I am executed: 3
Time Taken: 2.002072334289551
I am executed: 2
Time Taken: 1.001115083694458
I am executed: 1
Time Taken: 4.001702070236206
I am executed: 4
I am executed: 1
Time Taken: 3.0030171871185303
I am executed: 3
注意: LRUCache 也可以从标准 Python 包——functools 调用。它可以被导入为
from functools import lru_cache
@lru_cache
def myfunc():
pass
TTLCache
TTLCache 或“生存时间”缓存是 cachetools 模块中包含的第三个功能。它需要两个参数——“max size”和“TTL”。“maxsize”的使用与 LRUCache 相同，但这里“TTL”的值表示缓存应该存储多长时间。该值以秒为单位。
语法:
@cached(cache= TTLCache(maxsize= 33, ttl = 600))
def some_fun():
pass
示例:
from cachetools import cached, TTLCache
import time
# Here recent 32 functions
# will we stored for 1 minutes
@cached(cache = TTLCache(maxsize = 32, ttl = 60))
def myfun(n):
# This delay resembles some task
s = time.time()
time.sleep(n)
print("\nTime Taken: ", time.time() - s)
return (f"I am executed: {n}")
print(myfun(3))
print(myfun(3))
time.sleep(61)
print(myfun(3))
输出:
Time Taken: 3.0031025409698486
I am executed: 3
I am executed: 3
Time Taken: 3.0029332637786865
I am executed: 3
lrucache
LFUCache 或“最少使用”缓存是另一种类型的缓存技术，用于检索项目被调用的频率。它丢弃最少被调用的项目，以便在必要时腾出空间。它需要一个参数——“max size”，与 LRUCache 中的参数相同。
语法:
@cached(cache= LFUCache(maxsize= 33))
def some_fun():
pass
示例:
from cachetools import cached, LFUCache
import time
# Here if a particular item is not called
# within 5 successive call of the function,
# it will be discarded
@cached(cache = LFUCache(maxsize = 5))
def myfun(n):
# This delay resembles some task
s = time.time()
time.sleep(n)
print("\nTime Taken: ", time.time() - s)
return (f"I am executed: {n}")
print(myfun(3))
print(myfun(3))
print(myfun(2))
print(myfun(4))
print(myfun(1))
print(myfun(1))
print(myfun(3))
print(myfun(3))
print(myfun(4))
输出:
Time Taken: 3.002413272857666
I am executed: 3
I am executed: 3
Time Taken: 2.002107620239258
I am executed: 2
Time Taken: 4.003819465637207
I am executed: 4
Time Taken: 1.0010886192321777
I am executed: 1
I am executed: 1
I am executed: 3
I am executed: 3
I am executed: 4
rcache
RRCache 或“随机替换”缓存是另一种类型的缓存技术，它会随机选择缓存中的项目，并在必要时将其丢弃以释放空间。它需要一个参数——“max size”，与 LRUCache 中的参数相同。它还有一个默认设置为“random.choice”的参数选项。
语法:
@cached(cache= RRCache(maxsize= 33))
def some_fun():
pass
示例:
from cachetools import cached, RRCache
import time
# Here if a particular item is not called
# within 5 successive call of the function,
# it will be discarded
@cached(cache = RRCache(maxsize = 5))
def myfun(n):
# This delay resembles some task
s = time.time()
time.sleep(n)
print("\nTime Taken: ", time.time() - s)
return (f"I am executed: {n}")
print(myfun(3))
print(myfun(3))
print(myfun(2))
print(myfun(4))
print(myfun(1))
print(myfun(1))
print(myfun(3))
print(myfun(2))
print(myfun(3))
输出:
Time Taken: 3.003124713897705
I am executed: 3
I am executed: 3
Time Taken: 2.0021231174468994
I am executed: 2
Time Taken: 4.004120588302612
I am executed: 4
Time Taken: 1.0011250972747803
I am executed: 1
I am executed: 1
I am executed: 3
I am executed: 2
I am executed: 3
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