删除列表中的所有对象 [英] Delete all objects in a list

问题描述

我创建了许多对象，然后将它们存储在列表中.但是我想在一段时间后删除它们，因为我创建了一个新闻，并且不希望我的内存过高(在我的情况下，如果不删除它，它会跳到20 gigs的内存).

I create many object then I store in a list. But I want to delete them after some time because I create news one and don't want my memory goes high (in my case, it jumps to 20 gigs of ram if I don't delete it).

这里有一些代码来说明我要做什么:

Here is a little code to illustrate what I trying to do:

class test:
    def __init__(self):
        self.a = "Hello World"
    def kill(self):
        del self

a = test()
b = test()
c = [a,b]

print("1)Before:",a,b)

for i in c:
    del i

for i in c:
    i.kill()   

print("2)After:",a,b)

A和B是我的对象. C是这两个对象的列表.我正在尝试使用C中的for循环将其删除:一次是使用DEL，另一次是使用一个函数.似乎不起作用，因为打印物继续显示对象.

A and B are my objects. C is a list of these two objects. I'm trying to delete it definitely with a for-loop in C: one time with DEL and other time with a function. It's not seem to work because the print continue to show the objects.

我需要这个，因为我多次创建了100 000个对象.第一次创建100k对象，第二次创建另一个100k，但是我不需要保留前一个100k.如果我不删除它们，则内存使用率会非常高，而且很快.

I need this because I create 100 000 objects many times. The first time I create 100k object, the second time another 100k but I don't need to keep the previous 100k. If I don't delete them, the memory usage goes really high, very quickly.

推荐答案

tl; dr;

mylist.clear()  # Added in python3.(? maybe 5?)
del mylist[:]

可能是执行此操作的最佳方法.该答案的其余部分试图解释为什么您的其他一些努力没有奏效.

are probably the best ways to do this. The rest of this answer tries to explain why some of your other efforts didn't work.

cpython至少在引用计数上起作用，以确定何时删除对象.在这里，您具有对相同对象的多个引用. a引用与c[0]引用相同的对象.当您遍历c(for i in c:)时，i在某些时候还引用了同一对象. del关键字会删除一个引用，因此:

cpython at least works on reference counting to determine when objects will be deleted. Here you have multiple references to the same objects. a refers to the same object that c[0] references. When you loop over c (for i in c:), at some point i also refers to that same object. the del keyword removes a single reference, so:

for i in c:
   del i

在c中创建对对象的引用，然后删除该引用-但该对象仍具有其他引用(例如，一个引用存储在c中)，因此它将持久存在.

creates a reference to an object in c and then deletes that reference -- but the object still has other references (one stored in c for example) so it will persist.

以相同的方式:

def kill(self):
    del self

仅删除该方法中对对象的引用.从列表中删除所有引用的一种方法是使用切片分配:

only deletes a reference to the object in that method. One way to remove all the references from a list is to use slice assignment:

mylist = list(range(10000))
mylist[:] = []
print(mylist)

显然，您也可以删除切片以删除就位的对象:

Apparently you can also delete the slice to remove objects in place:

del mylist[:]  #This will implicitly call the `__delslice__` or `__delitem__` method.

这将从mylist中删除所有引用，也将从所有引用mylist的引用中删除引用.与简单删除列表相比-例如

This will remove all the references from mylist and also remove the references from anything that refers to mylist. Compared that to simply deleting the list -- e.g.

mylist = list(range(10000))
b = mylist
del mylist
#here we didn't get all the references to the objects we created ...
print(b) #[0, 1, 2, 3, 4, ...]

最后，最近的python版本添加了 clear del mylist[:]相同的方法.

Finally, more recent python revisions have added a clear method which does the same thing that del mylist[:] does.

mylist = [1, 2, 3]
mylist.clear()
print(mylist)

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