app.py

import streamlit as st
import spacy
import numpy as np
from gensim import corpora, models
from itertools import chain
from sklearn.preprocessing import MultiLabelBinarizer
from sklearn.metrics.pairwise import cosine_similarity
from itertools import islice
from scipy.signal import argrelmax

nlp = spacy.load('en_core_web_sm')


def window(seq, n=3):
    it = iter(seq)
    result = tuple(islice(it, n))
    if len(result) == n:
        yield result
    for elem in it:
        result = result[1:] + (elem,)
        yield result
        
def get_depths(scores):
   
    def climb(seq, i, mode='left'):

        if mode == 'left':
            while True:
                curr = seq[i]
                if i == 0:
                    return curr
                i = i-1
                if not seq[i] > curr:
                    return curr

        if mode == 'right':
            while True:
                curr = seq[i]
                if i == (len(seq)-1):
                    return curr
                i = i+1
                if not seq[i] > curr:
                    return curr
    
    depths = []
    for i in range(len(scores)):
        score = scores[i]
        l_peak = climb(scores, i, mode='left')
        r_peak = climb(scores, i, mode='right')
        depth = 0.5 * (l_peak + r_peak - (2*score))
        depths.append(depth)
        
    return np.array(depths)


def get_local_maxima(depth_scores, order=1):
    maxima_ids = argrelmax(depth_scores, order=order)[0]
    filtered_scores = np.zeros(len(depth_scores))
    filtered_scores[maxima_ids] = depth_scores[maxima_ids]
    return filtered_scores

def compute_threshold(scores):
    s = scores[np.nonzero(scores)]
    threshold = np.mean(s) - (np.std(s) / 2)
    return threshold

def get_threshold_segments(scores, threshold=0.1):
    segment_ids = np.where(scores >= threshold)[0]
    return segment_ids


def print_list(lst):
    for e in lst:
        st.markdown("- " + e)


st.subheader("Topic Modeling with Segmentation")
uploaded_file = st.file_uploader("choose a text file", type=["txt"])
if uploaded_file is not None: 
    st.session_state["text"] = uploaded_file.getvalue().decode('utf-8')

st.write("OR")

input_text = st.text_area(
    label="Enter text separated by newlines",
    value="",
    key="text",
    height=150
)

button=st.button('Get Segments')
if (button==True) and input_text != "":
    texts = input_text.split('\n')
    sents = []
    for text in texts:
        doc = nlp(text)
        for sent in doc.sents:
            sents.append(sent)
    MIN_LENGTH = 3
    tokenized_sents = [[token.lemma_.lower() for token in sent if 
                        not token.is_stop and not token.is_punct and token.text.strip() and len(token) >= MIN_LENGTH] 
                        for sent in sents]
    st.write("Modeling topics:")


    np.random.seed(123)

    N_TOPICS = 5
    N_PASSES = 5

    dictionary = corpora.Dictionary(tokenized_sents)
    bow = [dictionary.doc2bow(sent) for sent in tokenized_sents]
    topic_model = models.LdaModel(corpus=bow, id2word=dictionary, num_topics=N_TOPICS, passes=N_PASSES)
    st.write("inferring topics ...")
    THRESHOLD = 0.05
    doc_topics = list(topic_model.get_document_topics(bow, minimum_probability=THRESHOLD))
    k = 3
    top_k_topics = [[t[0] for t in sorted(sent_topics, key=lambda x: x[1], reverse=True)][:k] 
                    for sent_topics in doc_topics]
    WINDOW_SIZE = 3
    window_topics = window(top_k_topics, n=WINDOW_SIZE)
    window_topics = [list(set(chain.from_iterable(window))) for window in window_topics]

    binarizer = MultiLabelBinarizer(classes=range(N_TOPICS))

    encoded_topic = binarizer.fit_transform(window_topics)
    st.write("generating segments ...")
    sims_topic = [cosine_similarity([pair[0]], [pair[1]])[0][0] for pair in zip(encoded_topic, encoded_topic[1:])]
    depths_topic = get_depths(sims_topic)
    filtered_topic = get_local_maxima(depths_topic, order=1)
    threshold_topic = compute_threshold(filtered_topic)
    threshold_segments_topic = get_threshold_segments(filtered_topic, threshold_topic)

    segment_ids = threshold_segments_topic + WINDOW_SIZE

    segment_ids = [0] + segment_ids.tolist() + [len(sents)]
    slices = list(zip(segment_ids[:-1], segment_ids[1:]))

    segmented = [sents[s[0]: s[1]] for s in slices]

    for segment in segmented[:-1]:
        print_list([s.text for s in segment])
        st.markdown("""---""")
        
    print_list([s.text for s in segmented[-1]])