Processing text using NLP | Basics

In this article, we will be learning the steps followed to process the text data before using it to train the actual Machine Learning Model.

Importing Libraries

The following must be installed in the current working environment:

• NLTK Library: The NLTK library is a collection of libraries and programs written for processing of English language written in Python programming language.
• urllib library: This is a URL handling library for python.
• BeautifulSoup library: This is a library used for extracting data out of HTML and XML documents.

Python3

import nltk
from bs4 import BeautifulSoup
from urllib.request import urlopen

Once importing all the libraries, we need to extract the text. Text can be in string datatype or a file that we have to process.

Extracting Data

For this article, we are using web scraping to read a webpage then we will be using get_text() function for changing it to str format.

Python3

raw = urlopen("https://www.w3.org/TR/PNG/iso_8859-1.txt").read()

raw1 = BeautifulSoup(raw)
raw2 = raw1.get_text()
raw2

Output :

Data Preprocessing

Once the data extraction is done, the data is now ready to process. For that follow these steps :

1. Deletion of Punctuations and numerical text

Python3

# deletion of punctuations and numerical values
def punc(raw2):
  raw2 = re.sub('[^a-zA-Z]', ' ', raw2)
  return raw2

2. Creating Tokens

Python3

# extracting tokens
def token(raw2):
  tokens = nltk.word_tokenize(raw2)
  return tokens

3. Removing Stopwords

Python3

# lowercase the letters
# removing stopwords
def remove_(tokens):
  final = [word.lower()
         for word in tokens if word not in stopwords.words("english")]
  return final

4. Lemmatization

Python3

# Lemmatizing
from textblob import TextBlob

def lemma(final):
  # initialize an empty string
  str1 = ' '.join(final)
  s = TextBlob(str1)
  lemmatized_sentence = " ".join([w.lemmatize() for w in s.words])
  return final

5. Joining the final tokens

Python3

# Joining the final results
def join_(final):
  review = ' '.join(final)
  return ans

To execute the above functions refer this code : 

Python3

# Calling all the functions
raw2 = punc(raw2)
tokens = token(raw2)
final = remove_(tokens)
final = lemma(final)
ans = join_(final)
ans

Output :