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Python Cachetools用法及代碼示例


Cachetools 是一個 Python 模塊，提供各種 memory 集合和裝飾器。它還包括 functools 的 @lru_cache 裝飾器的變體。要使用它，首先我們需要使用 pip 安裝它。

pip install cachetools

Cachetools為我們提供了五個主要函數。

  • cached
  • LRUCache
  • TTLCache
  • LFUCache
  • RRCache

讓我們通過示例詳細了解以下每個函數。

緩存

緩存用作裝飾器。當我們調用cache時，它會緩存該函數以供以後使用。默認情況下，這將執行簡單的緩存。

用法:

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

例子：讓我們用一個例子來看看。我們將使用時間模塊來查看模塊的效率。


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)

輸出：

9227465
Time Taken:  4.553245782852173
9227465
Time Taken(cached):  0.0003821849822998047

LRU緩存

LRUCache 在緩存裝飾器內部使用。 LRU緩存意味著“Least Recently Used”緩存。它需要一個參數“maxsize”，該參數表明應緩存最近的函數。

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))

輸出：

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緩存也可以從標準 Python 包 - functools 調用。它可以看到導入為

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

TTL緩存

TTLCache 或“Time To Live” 緩存是cachetools 模塊中包含的第三個函數。它需要兩個參數 - “maxsize” 和 “TTL”。 “maxsize” 的使用與 LRUCache 相同，但這裏 “TTL” 的值說明緩存應存儲多長時間。該值以秒為單位。

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))

輸出：

Time Taken:  3.0031025409698486
I am executed: 3
I am executed: 3

Time Taken:  3.0029332637786865
I am executed: 3

LFU緩存

LFUCache 或 “Least Frequently Used” 緩存是另一種類型的緩存技術，用於檢索某個項目的調用頻率。它會丟棄最不常調用的項目，以便在必要時騰出空間。它需要一個參數 - “maxsize”，與 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))

輸出：


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緩存

RRCache 或 “Random Replacement” 緩存是另一種類型的緩存技術，它隨機選擇緩存中的項目並在必要時丟棄它們以釋放空間。它需要一個參數 - “maxsize”，與 LRUCache 中的相同。它還具有一個參數選擇，默認設置為“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))

輸出：

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


相關用法


注：本文由純淨天空篩選整理自佚名大神的英文原創作品 Cachetools module in Python。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。