<p>我知道Python <code>dict</code>s在移除项时会“泄漏”(因为项的槽将被神奇的“removed”值覆盖)…但是<code>set</code>类的行为会相同吗?保持一个<code>set</code>在周围,随着时间的推移添加和删除内容是否安全?在</p>
<p><strong>编辑</strong>:好吧,我已经试过了,以下是我发现的:</p>
<pre>
>>> import gc
>>> gc.collect()
0
>>> nums = range(1000000)
>>> gc.collect()
0
### rsize: 20 megs
### A baseline measurement
>>> s = set(nums)
>>> gc.collect()
0
### rsize: 36 megs
>>> for n in nums: s.remove(n)
>>> gc.collect()
0
### rsize: 36 megs
### Memory usage doesn't drop after removing every item from the set…
>>> s = None
>>> gc.collect()
0
### rsize: 20 megs
### … but nulling the reference to the set *does* free the memory.
>>> s = set(nums)
>>> for n in nums: s.remove(n)
>>> for n in nums: s.add(n)
>>> gc.collect()
0
### rsize: 36 megs
### Removing then re-adding keys uses a constant amount of memory…
>>> for n in nums: s.remove(n)
>>> for n in nums: s.add(n+1000000)
>>> gc.collect()
0
### rsize: 47 megs
### … but adding new keys uses more memory.
</pre>
<p>对于这样的问题,最好先做一个这样的快速实验,看看会发生什么:</p>
<pre><code>s = set()
for a in range(1000):
for b in range(10000000):
s.add(b)
for b in range(10000000):
s.remove(b)
</code></pre>
<p>医生和人们所说的和实际的行为往往是不一致的。如果这对你很重要,测试一下。不要依赖别人。在</p>