安装
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pip <span class="hljs-keyword">install</span> pybloom |
该模块包含两个类实现布隆过滤器功能。
BloomFilter 是定容。
ScalableBloomFilter 可以自动扩容
使用
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<span class="hljs-meta">></span><span class="bash">>> from pybloom import BloomFilter</span> <span class="hljs-meta">></span><span class="bash">>> f = BloomFilter(capacity=1000, error_rate=0.001) <span class="hljs-comment"># capacity是容量, error_rate 是能容忍的误报率</span></span> <span class="hljs-meta">></span><span class="bash">>> f.add(<span class="hljs-string">'Traim304'</span>) <span class="hljs-comment"># 当不存在该元素,返回False</span></span> False <span class="hljs-meta">></span><span class="bash">>> f.add(<span class="hljs-string">'Traim304'</span>) <span class="hljs-comment"># 若存在,返回 True</span></span> True <span class="hljs-meta">></span><span class="bash">>> <span class="hljs-string">'Traim304'</span> <span class="hljs-keyword">in</span> f <span class="hljs-comment"># 值得注意的是若返回 True。该元素可能存在, 也可能不存在。过滤器能容许存在一定的错误</span></span> True <span class="hljs-meta">></span><span class="bash">>> <span class="hljs-string">'Jacob'</span> <span class="hljs-keyword">in</span> f <span class="hljs-comment"># 但是 False。则必定不存在</span></span> False <span class="hljs-meta">></span><span class="bash">>> len(f) <span class="hljs-comment"># 当前存在的元素</span></span> 1 <span class="hljs-meta"> ></span><span class="bash">>> f = BloomFilter(capacity=1000, error_rate=0.001) </span> <span class="hljs-meta">></span><span class="bash">>> from pybloom import ScalableBloomFilter</span> <span class="hljs-meta">></span><span class="bash">>> sbf = ScalableBloomFilter(mode=ScalableBloomFilter.SMALL_SET_GROWTH)</span> <span class="hljs-meta">></span><span class="bash">>> <span class="hljs-comment"># sbf.add() 与 BloomFilter 同</span></span> |
超过误报率时抛出异常
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>>> f = BloomFilter(capacity=<span class="hljs-number">1000</span>, error_rate=<span class="hljs-number">0.0000001</span>) >>> <span class="hljs-keyword">for</span> <span class="hljs-keyword">a</span> <span class="hljs-keyword">in</span> range(<span class="hljs-number">1000</span>): ... _ = f.<span class="hljs-built_in">add</span>(<span class="hljs-keyword">a</span>) ... >>> <span class="hljs-built_in">len</span>(<span class="hljs-keyword">a</span>) Traceback (most recent call <span class="hljs-keyword">last</span>): File <span class="hljs-string">"<stdin>"</span>, <span class="hljs-built_in">line</span> <span class="hljs-number">1</span>, <span class="hljs-keyword">in</span> <module> TypeError: object <span class="hljs-keyword">of</span> type <span class="hljs-string">'int'</span> has no <span class="hljs-built_in">len</span>() >>> <span class="hljs-built_in">len</span>(f) <span class="hljs-number">1000</span> >>> f.<span class="hljs-built_in">add</span>(<span class="hljs-number">1000</span>) False >>> f.<span class="hljs-built_in">add</span>(<span class="hljs-number">1001</span>) <span class="hljs-comment"># 当误报率超过 error_rate 会报错</span> Traceback (most recent call <span class="hljs-keyword">last</span>): File <span class="hljs-string">"<stdin>"</span>, <span class="hljs-built_in">line</span> <span class="hljs-number">1</span>, <span class="hljs-keyword">in</span> <module> File <span class="hljs-string">"/usr/local/lib/python2.7/site-packages/pybloom/pybloom.py"</span>, <span class="hljs-built_in">line</span> <span class="hljs-number">182</span>, <span class="hljs-keyword">in</span> <span class="hljs-built_in">add</span> raise IndexError(<span class="hljs-string">"BloomFilter is at capacity"</span>) IndexError: BloomFilter is <span class="hljs-keyword">at</span> capacity |
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