Regular Expressions (RegEx) - comments

A very insightful post @jasoleramos, thank you for sharing. I agree that RegEx analysis can be an extremely useful tool in identifying patterns within recurring document types in NLP applications. One example being in SEC 10-K Filings, where an analyst can leverage RegEx patterns to extract key financial data or information contained within 10-K filings in a systematic way, allowing to analyse 1000s of fillings at once in a seamless manner. Here's another example of RegEx analysis at work in the 10-K Filings example mentioned with the aim of extracting Items 1A, Item 7 and Item 7A from the filings as they are strategic for sentiment analysis, these sections are traditionally rich in information related to a company’s risk factors, management’s discussion of financial condition, and qualitative disclosures about market risk:

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import pandas as pd

import numpy as np

import time

import random

import requests

import re

from bs4 import BeautifulSoup

# request function

def send_request(url):

user_agents = [

"Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.124 Safari/537.36",

"Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:89.0) Gecko/20100101 Firefox/89.0",

]

headers = {'User-Agent': random.choice(user_agents)}

response = requests.get(url, headers=headers)

time.sleep(random.uniform(1, 3))

return response

# get filing data

def get_filing_html(cik_info, accession_number, filing_type, filing_date):

if filing_type != '10-K': # skip non-10-K

return None

url = f"https://www.sec.gov/Archives/edgar/data/{cik_info['cik']}/{accession_number.replace('-', '')}/{accession_number}.txt"

try:

response = send_request(url)

response.raise_for_status()

doc_text = response.text # extract text

return {

'CIK': cik_info['cik'],

'Ticker': cik_info['tickers'][0] if cik_info.get('tickers') else 'N/A', # get ticker

'Accession Number': accession_number,

'SIC Description': cik_info.get('sicDescription', 'N/A'), # get SIC

'Text Document': doc_text, # store text

'Filing Type': filing_type,

'Filing Date': filing_date

}

except requests.exceptions.RequestException as e:

print(f"Error: {e}")

return None

def extract_sentences(raw_10k):

# Regex patterns

doc_start_pattern = re.compile(r'<DOCUMENT>')

doc_end_pattern = re.compile(r'</DOCUMENT>')

type_pattern = re.compile(r'<TYPE>[^\n]+')

item_regex = re.compile(r'(>Item(\s|&#160;|&nbsp;)(1A|1B|7A|7|8)\.{0,1})|(ITEM\s(1A|1B|7A|7|8))')

# finding document start and end indices

doc_start_is = [x.end() for x in doc_start_pattern.finditer(raw_10k)]

doc_end_is = [x.start() for x in doc_end_pattern.finditer(raw_10k)]

doc_types = [x[len('<TYPE>'):] for x in type_pattern.findall(raw_10k)]

document = {}

# looping through each section type and save only the '10-K' section in dictionary

for doc_type, doc_start, doc_end in zip(doc_types, doc_start_is, doc_end_is):

if doc_type == '10-K':

document[doc_type] = raw_10k[doc_start:doc_end]

# finding matches using regex in '10-K' section

matches = item_regex.finditer(document.get('10-K', ''))

# creating a df from matches

item_df = pd.DataFrame([(x.group(), x.start(), x.end()) for x in matches], columns=['item', 'start', 'end'])

item_df['item'] = item_df['item'].str.lower()

# cleaning up unnecessary characters

item_df.replace('&#160;', ' ', regex=True, inplace=True)

item_df.replace('&nbsp;', ' ', regex=True, inplace=True)

item_df.replace(' ', '', regex=True, inplace=True)

item_df.replace('\.', '', regex=True, inplace=True)

item_df.replace('>', '', regex=True, inplace=True)

# dropping duplicates

pos_dat = item_df.sort_values('start', ascending=True).drop_duplicates(subset=['item'], keep='last')

# extracting content for each item

item_1a_raw = ''

item_7_raw = ''

item_7a_raw = ''

if 'item1a' in pos_dat['item'].values:

item_1a_start = pos_dat.loc[pos_dat['item'] == 'item1a', 'start'].values

item_1b_start = pos_dat.loc[pos_dat['item'] == 'item1b', 'start'].values

if item_1a_start.size > 0 and item_1b_start.size > 0:

item_1a_raw = document.get('10-K', '')[item_1a_start[0]:item_1b_start[0]]

if 'item7' in pos_dat['item'].values:

item_7_start = pos_dat.loc[pos_dat['item'] == 'item7', 'start'].values

item_7a_start = pos_dat.loc[pos_dat['item'] == 'item7a', 'start'].values

if item_7_start.size > 0 and item_7a_start.size > 0:

item_7_raw = document.get('10-K', '')[item_7_start[0]:item_7a_start[0]]

if 'item7a' in pos_dat['item'].values:

item_7a_start = pos_dat.loc[pos_dat['item'] == 'item7a', 'start'].values

item_8_start = pos_dat.loc[pos_dat['item'] == 'item8', 'start'].values

if item_7a_start.size > 0 and item_8_start.size > 0:

item_7a_raw = document.get('10-K', '')[item_7a_start[0]:item_8_start[0]]

# extracting sentences from BeautifulSoup objects

item_1a_content = BeautifulSoup(item_1a_raw, 'lxml').get_text()

item_7_content = BeautifulSoup(item_7_raw, 'lxml').get_text()

item_7a_content = BeautifulSoup(item_7a_raw, 'lxml').get_text()

# combining sentences from different items

all_sentences = f"{item_1a_content} {item_7_content} {item_7a_content}"

return all_sentences

# example usage

cik_info = {

'cik': '0000320193', # example CIK

'tickers': ['AAPL'], # example ticker

'sicDescription': 'Electronic Computers [3571]'

}

accession_number = '0001193125-11-282113'

filing_type = '10-K'

filing_date = '2011-10-26'

# get filing data

filing_data = get_filing_html(cik_info, accession_number, filing_type, filing_date)

if filing_data:

filing_data['Sentences'] = extract_sentences(filing_data['Text Document'])

print(pd.DataFrame([filing_data])[['CIK', 'Ticker', 'Filing Date', 'SIC Description', 'Sentences']])