How to print the LDA topics models from gensim? Py

Question

Using gensim I was able to extract topics from a set of documents in LSA but how do I access the topics generated from the LDA models?

When printing the lda.print_topics(10) the code gave the following error because print_topics() return a NoneType:

Traceback (most recent call last):
  File "/home/alvas/workspace/XLINGTOP/xlingtop.py", line 93, in <module>
    for top in lda.print_topics(2):
TypeError: 'NoneType' object is not iterable

The code:

from gensim import corpora, models, similarities
from gensim.models import hdpmodel, ldamodel
from itertools import izip

documents = ["Human machine interface for lab abc computer applications",
              "A survey of user opinion of computer system response time",
              "The EPS user interface management system",
              "System and human system engineering testing of EPS",
              "Relation of user perceived response time to error measurement",
              "The generation of random binary unordered trees",
              "The intersection graph of paths in trees",
              "Graph minors IV Widths of trees and well quasi ordering",
              "Graph minors A survey"]

# remove common words and tokenize
stoplist = set('for a of the and to in'.split())
texts = [[word for word in document.lower().split() if word not in stoplist]
         for document in documents]

# remove words that appear only once
all_tokens = sum(texts, [])
tokens_once = set(word for word in set(all_tokens) if all_tokens.count(word) == 1)
texts = [[word for word in text if word not in tokens_once]
         for text in texts]

dictionary = corpora.Dictionary(texts)
corpus = [dictionary.doc2bow(text) for text in texts]

# I can print out the topics for LSA
lsi = models.LsiModel(corpus_tfidf, id2word=dictionary, num_topics=2)
corpus_lsi = lsi[corpus]

for l,t in izip(corpus_lsi,corpus):
  print l,"#",t
print
for top in lsi.print_topics(2):
  print top

# I can print out the documents and which is the most probable topics for each doc.
lda = ldamodel.LdaModel(corpus, id2word=dictionary, num_topics=50)
corpus_lda = lda[corpus]

for l,t in izip(corpus_lda,corpus):
  print l,"#",t
print

# But I am unable to print out the topics, how should i do it?
for top in lda.print_topics(10):
  print top

Answer 1

Recently, came across a similar issue while working with Python 3 and Gensim 2.3.0. print_topics() and show_topics() weren't giving any error but also not printing anything. Turns out that show_topics() returns a list. So one can simply do:

topic_list = show_topics()
print(topic_list)

Answer 2

You can also export the top words from each topic to a csv file. topn controls how many words under each topic to export.

import pandas as pd

top_words_per_topic = []
for t in range(lda_model.num_topics):
    top_words_per_topic.extend([(t, ) + x for x in lda_model.show_topic(t, topn = 5)])

pd.DataFrame(top_words_per_topic, columns=['Topic', 'Word', 'P']).to_csv("top_words.csv")

The CSV file has the following format

Topic Word  P  
0     w1    0.004437  
0     w2    0.003553  
0     w3    0.002953  
0     w4    0.002866  
0     w5    0.008813  
1     w6    0.003393  
1     w7    0.003289  
1     w8    0.003197 
...