Philadelphia Reflections

The musings of a physician who has served the community for over six decades

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TF-IDF in Python and MySQL

TF-IDF: Term Frequency-Inverse Document Frequency

Using Python and Scikit-Learn to analyze blogs in a MySQL database

Downloaded from a jupyter notebook into *.py format


import mysql.connector
import re
import pandas as pd
import numpy as np


# dict to group blogs by keywords

from collections import defaultdict
d = defaultdict(list)


# everything

plot_title = "Non-Terse-Verse Philadelphia Reflections"

query = '''SELECT title, blog_contents, table_key 
                   FROM individual_reflections
                  WHERE LOWER(title) NOT LIKE '%terse%' AND 
                     LOWER(title) NOT LIKE '%znote%' AND
                     LOWER(title) NOT LIKE '%front stuff%' '''

def remove_html_tags(text):
    """Remove html tags from a string"""
    import re
    clean = re.compile('<.*?>')
    step1 = re.sub(clean, ' ', text)
    step2 = step1.replace('\n', ' ').replace('\r', '')
    step3 = ' '.join(step2.split())
    
    text=step3.lower()
    text=re.sub("","",text)
    text=re.sub("(\\d|\\W)+"," ",text)
    text=text.strip()
    
    return text

mydb = mysql.connector.connect(
  host="",
  user="",
  passwd="",
    database=''
)
cursor = mydb.cursor()

cursor.execute(query)

df_idf = pd.DataFrame([])

for (title, blog_contents, table_key) in cursor:
    blog_contents = remove_html_tags(blog_contents)
    title = remove_html_tags(title)
    df_idf = df_idf.append(pd.DataFrame({'table_key': table_key, 'title': title, 'body': blog_contents}, index=[0]), ignore_index=True)
    
df_idf['text'] = df_idf['title'] + " " + df_idf['body']

docs_test = df_idf['text'].tolist()

cursor.close()
mydb.close()

df_idf.head()


from sklearn.feature_extraction.text import CountVectorizer
import re
 
 
#get the text column 
docs=df_idf['text'].tolist()
 
#create a vocabulary of words, 
#ignore words that appear in 85% of documents, 
#eliminate stop words
cv=CountVectorizer(max_df=0.85,stop_words='english',max_features=10000)  # cv = cv
word_count_vector=cv.fit_transform(docs)                                 # cv_fit = word_count_vector
list(cv.vocabulary_.keys())[:10]


from sklearn.feature_extraction.text import TfidfTransformer
 
tfidf_transformer=TfidfTransformer(smooth_idf=True,use_idf=True)
tfidf_transformer.fit(word_count_vector)


def sort_coo(coo_matrix):
    tuples = zip(coo_matrix.col, coo_matrix.data)
    return sorted(tuples, key=lambda x: (x[1], x[0]), reverse=True)
 
def extract_topn_from_vector(feature_names, sorted_items, topn=10):
    """get the feature names and tf-idf score of top n items"""
    
    #use only topn items from vector
    sorted_items = sorted_items[:topn]
 
    score_vals = []
    feature_vals = []
    
    # word index and corresponding tf-idf score
    for idx, score in sorted_items:
        
        #keep track of feature name and its corresponding score
        score_vals.append(round(score, 3))
        feature_vals.append(feature_names[idx])
 
    #create a tuples of feature,score
    #results = zip(feature_vals,score_vals)
    results= {}
    for idx in range(len(feature_vals)):
        results[feature_vals[idx]]=score_vals[idx]
    
    return results


# mapping of index 
feature_names=cv.get_feature_names()

# human-readable list of keywords for each blog
myfile = open('.../tf-idf.txt', 'w')

# explode-able/split-able list of keywords for each blog
kwfile = open('.../kwds.txt', 'w')

header = '''
==========================================
10 most-significant keywords for each blog
=========================================='''
print(header)
myfile.write(header+"\n")

for i in range(len(docs)):
 
    # get the document that we want to extract keywords from
    doc=docs[i]

    #generate tf-idf for the given document
    tf_idf_vector=tfidf_transformer.transform(cv.transform([doc]))

    #sort the tf-idf vectors by descending order of scores
    sorted_items=sort_coo(tf_idf_vector.tocoo())

    #extract only the top n; n here is 10
    keywords=extract_topn_from_vector(feature_names,sorted_items,10)

    # now print the results
    print("\n=====Title=====")
    myfile.write("\n=====Title=====\n")
    
    print(df_idf.iloc[i]['table_key'], df_idf.iloc[i]['title'])
    myfile.write("{} {}\n".format(df_idf.iloc[i]['table_key'],df_idf.iloc[i]['title']))
    
    kwds = str(df_idf.iloc[i]['table_key'])+'|'
    
    print("\n===Keywords===")
    myfile.write("\n===Keywords===\n")
    for k in keywords:
        print(k,keywords[k])
        d[k].append((df_idf.iloc[i]['table_key'],
                     keywords[k],
                     df_idf.iloc[i]['title']))
        myfile.write("{} {}\n".format(k,keywords[k]))
        kwds += k+','
    kwfile.write(kwds[:-1]+"\n")
        
myfile.close()
kwfile.close()



import operator

word_list = cv.get_feature_names();    
count_list = word_count_vector.toarray().sum(axis=0) 

word_freq = sorted(dict(zip(word_list,count_list)).items(), key=operator.itemgetter(1), reverse=True)

x = []
y = []
for word,freq in word_freq[:25]:
    x.append(word)
    y.append(freq)
    
from matplotlib import pyplot as plt
plt.figure(figsize=(15,15))
plt.plot(x,y)
plt.title("Word Frequency in "+plot_title,fontsize=18)
plt.xticks(rotation=45,fontsize=18)
plt.yticks(fontsize=18)
plt.grid()
plt.show()
plt.savefig('.../Word_Frequency.png')


# # Group blogs by keywords


myfile = open('.../Keyword_Popularity.txt', 'w')

header = '''
==================================================
Most-Frequent Keywords with the blogs they specify
==================================================
   (blog key, keyword importance, blog title)
..................................................\n'''
print(header)
myfile.write(header+"\n")

x = []
y = []

for k in sorted(d, key=lambda k: len(d[k]), reverse=True):
    if len(d[k]) == 1: break
    x.append(k)
    y.append(len(d[k]))
    print(len(d[k]),"blogs contain the keyword","'"+k+"'")
    myfile.write("{} blogs contain the keyword '{}'\n".format(len(d[k]), k))
    print('---------------------------------------------')
    myfile.write("---------------------------------------------\n")
    for t in sorted(d[k], key=lambda tup:(-tup[1], tup[2])):
        print(t)
        myfile.write("{}\n".format(t))
    print ('*****\n')
    myfile.write('*****\n\n')
    
myfile.close()


num = 50

plt.figure(figsize=(15,15))
plt.plot(x[:num],y[:num])
plt.title(str(num)+" Most Popular Keywords in "+plot_title,fontsize=18)
plt.xticks(rotation=90,fontsize=12)
plt.yticks(fontsize=18)
plt.ylabel("Number of blogs with this keyword",fontsize=18)

plt.grid()

plt.savefig('.../Keyword_Popularity.png')
plt.show()

 

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