How to use the gc module for garbage collection in Python 3.x

How to use the gc module for garbage collection in Python 3.x

Introduction: In Python programming, garbage collection (Garbage Collection, referred to as GC) is an important task, it can automatically release no longer Used memory space to improve program performance and efficiency. The gc module in Python provides some powerful tools to help us manage memory and perform garbage collection. This article will introduce how to use the gc module in Python 3.x for garbage collection and provide corresponding code examples.

1. Introducing the gc module
   Before we start using the gc module, we need to introduce it first. In Python, modules are introduced using the import keyword. The specific sample code is as follows:

   import gc

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2. Turn on and set up garbage collection
   The gc module provides some functions and variables to control the behavior of garbage collection. You can use the gc.enable() function to turn on garbage collection, and use the gc.disable() function to turn off garbage collection. For example:

   gc.enable()  # 开启垃圾回收
   gc.disable()  # 关闭垃圾回收

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   In addition, you can use the gc.set_threshold() function to set the garbage collection threshold. A threshold is usually a tuple of integer values ​​that controls the frequency and magnitude of garbage collection. The sample code is as follows:

   gc.set_threshold(700, 10, 5)

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   In the above example, the first parameter indicates that when the number of objects to be allocated increases to 700, a garbage collection will be performed; the second parameter indicates that each time the garbage collection is triggered, it will be cleaned up At least 10 objects; the third parameter indicates that when the number of garbage collection triggers reaches 5 times, a very aggressive recycling cycle will be started.

3. Force Garbage Collection
   In some cases, we may want to force garbage collection even if the threshold is not reached. The gc module provides the gc.collect() function to manually trigger garbage collection. The specific sample code is as follows:

   gc.collect()

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   Forcing garbage collection is usually not necessary because Python's garbage collector will automatically collect it.

4. Getting and printing object reference counts
   The gc module provides the gc.get_referrers() function and gc.get_referents() function to obtain the reference count information of the object. The specific sample code is as follows:

   import sys
   
   # 定义一个函数用于测试
   def test():
    a = [1, 2, 3]
    b = [a, a]
    print(sys.getrefcount(a))
   
   # 执行测试函数
   test()

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