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Python Cachetools用法及代码示例


Cachetools 是一个 Python 模块，提供各种 memory 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函数。

  • cached
  • LRUCache
  • TTLCache
  • LFUCache
  • RRCache

让我们通过示例详细了解以下每个函数。

缓存

缓存用作装饰器。当我们调用cache时，它会缓存该函数以供以后使用。默认情况下，这将执行简单的缓存。

用法:

@cached(cache = {})
def some_fun():
    pass

例子：让我们用一个例子来看看。我们将使用时间模块来查看模块的效率。


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

LRU缓存

LRUCache 在缓存装饰器内部使用。 LRU缓存意味着“Least Recently Used”缓存。它需要一个参数“maxsize”，该参数表明应缓存最近的函数。

用法:

@cached(cache= LRUCache(maxsize= 3))
def some_fun():
    pass

例子：


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： LRU缓存也可以从标准 Python 包 - functools 调用。它可以看到导入为

from functools import lru_cache
@lru_cache
def myfunc():
    pass

TTL缓存

TTLCache 或“Time To Live” 缓存是cachetools 模块中包含的第三个函数。它需要两个参数 - “maxsize” 和 “TTL”。 “maxsize” 的使用与 LRUCache 相同，但这里 “TTL” 的值说明缓存应存储多长时间。该值以秒为单位。

用法:

@cached(cache= TTLCache(maxsize= 33, ttl = 600))
def some_fun():
    pass

例子：


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

LFU缓存

LFUCache 或 “Least Frequently Used” 缓存是另一种类型的缓存技术，用于检索某个项目的调用频率。它会丢弃最不常调用的项目，以便在必要时腾出空间。它需要一个参数 - “maxsize”，与 LRUCache 中的相同。

用法:

@cached(cache= LFUCache(maxsize= 33))
def some_fun():
    pass

例子：


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

RR缓存

RRCache 或 “Random Replacement” 缓存是另一种类型的缓存技术，它随机选择缓存中的项目并在必要时丢弃它们以释放空间。它需要一个参数 - “maxsize”，与 LRUCache 中的相同。它还具有一个参数选择，默认设置为“random.choice”。

用法:

@cached(cache= RRCache(maxsize= 33))
def some_fun():
    pass

例子：


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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注：本文由纯净天空筛选整理自佚名大神的英文原创作品 Cachetools module in Python。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。