bm25的python代码
时间: 2023-09-03 19:15:38 浏览: 55
以下是BM25的Python代码示例:
```python
import math
class BM25:
def __init__(self, corpus, k1=1.5, b=0.75):
self.corpus_size = len(corpus)
self.avgdl = sum(len(x) for x in corpus) / self.corpus_size
self.k1 = k1
self.b = b
self.doc_freqs = []
self.idf = {}
self.doc_len = []
for document in corpus:
frequencies = {}
length = len(document)
self.doc_len.append(length)
for word in document:
if word not in frequencies:
frequencies[word] = 0
frequencies[word] += 1
self.doc_freqs.append(frequencies)
for word, freq in frequencies.items():
if word not in self.idf:
self.idf[word] = 0
self.idf[word] += 1
for word, freq in self.idf.items():
self.idf[word] = math.log(self.corpus_size - freq + 0.5) - math.log(freq + 0.5)
def get_score(self, query, index, average_idf):
score = 0
doc_freqs = self.doc_freqs[index]
for term in query:
if term not in doc_freqs:
continue
numerator = (self.k1 + 1) * doc_freqs[term]
denominator = self.k1 * ((1 - self.b) + self.b * (self.doc_len[index] / self.avgdl)) + doc_freqs[term]
score += self.idf[term] * (numerator / denominator)
return score
def get_scores(self, query):
query_toks = query.split()
scores = [0] * self.corpus_size
for index in range(self.corpus_size):
score = self.get_score(query_toks, index, self.avgdl)
scores[index] = score
return scores
```
这是一个简单的实现,可以根据需要进行修改。要使用它,首先需要将文本语料库(即所有文档的集合)作为列表传递给BM25类的构造函数。然后,可以使用“get_scores”方法来获得查询与每个文档的相关分数。
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