Python文本相似度详解

Python是一种流行的编程语言，具有易于使用的语言结构， 因此在自然语言处理(NLP)中备受欢迎。在本文中，我们将介绍Python中文本相似度的计算方法，包括文本相似度计算、文档相似度、文本匹配、相似度分析、文本进度条注释等方面。

一、Python文本相似度计算

文本相似度计算是一种常见的NLP任务。在Python中，我们可以使用NLTK(Natural Language Toolkit)等库来完成这项任务。以下是一个计算文本相似度的示例代码：

import nltk
from nltk.tokenize import word_tokenize
from nltk.corpus import stopwords
from nltk.stem import PorterStemmer
from nltk.stem import WordNetLemmatizer
from sklearn.metrics.pairwise import cosine_similarity

# 从文本中提取文本特征
def extract_features(text):
    # 令牌化并去除停用词
    stop_words = set(stopwords.words('english'))
    words = [word for word in word_tokenize(text.lower()) if word.isalpha() and word not in stop_words]
    #stemming
    stemmer = PorterStemmer()
    words = [stemmer.stem(word) for word in words]
    #lemmatization
    lemmatizer = WordNetLemmatizer()
    words = [lemmatizer.lemmatize(word) for word in words]
    #返回所有单词的列表
    return words

# 计算文本相似度
def calculate_similarity(text1,text2):
    #提取文本特征
    text1_words = extract_features(text1)
    text2_words = extract_features(text2)

    #将提取出的文本特征转换成向量
    all_words = list(set(text1_words + text2_words))
    text1_vector = [text1_words.count(word) for word in all_words]
    text2_vector = [text2_words.count(word) for word in all_words]

    # 计算余弦相似度
    cosine_sim = cosine_similarity([text1_vector],[text2_vector])[0][0]
    return cosine_sim

#测试
text1 = "Python is a popular programming language."
text2 = "Python is commonly used in natural language processing."
print("Similarity score:",calculate_similarity(text1,text2))

二、Python文档相似度

文档相似度是指计算两篇文档之间的相似度。在Python中，我们可以使用gensim等库来实现这一任务。以下是一个计算文档相似度的示例代码：

import gensim
from gensim import corpora, similarities

#处理文本并将其转换成相应的向量表示形式
def prepare_corpus(docs):
    stoplist = set('for a of the and to in'.split())
    texts = [[word for word in doc.lower().split() if word not in stoplist] for doc in docs]
    dictionary = corpora.Dictionary(texts)
    corpus = [dictionary.doc2bow(text) for text in texts]

    #tf-idf
    tfidf = models.TfidfModel(corpus)

    #将文档向量化
    corpus_tfidf = tfidf[corpus]

    return dictionary,corpus_tfidf

#计算文档相似度
def calculate_similarity(docs):
    dictionary,corpus_tfidf = prepare_corpus(docs)

    #将语料库转换成lsi模型
    lsi = models.LsiModel(corpus_tfidf,id2word=dictionary,num_topics=2)

    #计算相似性
    index = similarities.MatrixSimilarity(lsi[corpus_tfidf])

    #返回相似度矩阵
    return index

#测试
docs = ["Python is a popular programming language used in natural language processing",
        "Natural language processing is a subfield of computer science and artificial intelligence",
        "Python is useful for web development and scientific computing"]
index = calculate_similarity(docs)
sims = index[lsi[corpus_tfidf]]
print(list(enumerate(sims)))

三、Python文本相似度匹配

文本匹配是指在给定一组文本和一个查询文本的情况下，找到与查询文本最相似的文本。在Python中，我们可以使用fuzzywuzzy等库来完成这项任务。以下是一个计算文本匹配度的示例代码：

from fuzzywuzzy import fuzz

# 计算字符串相似度
def calculate_similarity(str1,str2):
    # 计算jaro_winkler系数
    jaro_winkler = fuzz.jaro_winkler(str1,str2)
    return jaro_winkler

#测试
str1 = "Python is a popular programming language."
str2 = "Python is used for web development and scientific computing."
print("Similarity score:",calculate_similarity(str1,str2))

四、Python相似度分析

相似度分析是指使用文本相似度来分析文本并从中提取有意义的信息。在Python中，我们可以使用pandas等库来完成这项任务。以下是几个分析篇幅相似度的示例代码：

import pandas as pd
import numpy as np

# 进行数据分析
def analyze_similarity(df):
    #计算相似度矩阵
    similarity_matrix = np.zeros([len(df),len(df)])
    for i in range(len(df)):
        for j in range(i,len(df)):
            similarity_matrix[i][j] = calculate_similarity(df.iloc[i]['text'],df.iloc[j]['text'])
            similarity_matrix[j][i] = similarity_matrix[i][j]

    #转换为DataFrame
    df_similarity = pd.DataFrame(similarity_matrix,index=df['id'],columns=df['id'])

    #筛选相似度大于等于0.7的文章
    mask = df_similarity >= 0.7
    df_pairs = pd.DataFrame({'id1':df_similarity[mask].stack().index.get_level_values('level_0'),
                             'id2':df_similarity[mask].stack().index.get_level_values('level_1')}).drop_duplicates()

    #返回符合条件的文章
    return df_pairs

#测试
df = pd.DataFrame({'id':[1,2,3],
                   'text':["Python is a popular programming language.",
                           "Python is used for web development and scientific computing.",
                           "Natural language processing is a subfield of computer science and artificial intelligence."]})
df_pairs = analyze_similarity(df)
print(df_pairs)

五、Python文本进度条注释

在Python中，我们可以使用tqdm等库来为某些长时间运行的任务添加进度条注释。以下是一个将文本向量化过程添加进度条注释的示例代码：

from tqdm import tqdm

#将文本向量化并显示进度条注释
def vectorize_text(docs):
    vectors = []
    for doc in tqdm(docs):
        vector = extract_features(doc)
        vectors.append(vector)
    
    return vectors

#测试
docs = ["Python is a popular programming language.",
        "Natural language processing is a subfield of computer science and artificial intelligence.",
        "Python is used for web development and scientific computing."]
vectors = vectorize_text(docs)
print(vectors)