Python: Get text between two strings, characters, or delimiters

When we are performing data cleaning, data manipulation or data wrangling we need to extract a text between strings, characters or delimiters. In this blog post we will explore different methods to extract text between two strings in Python. We will see approaches for handling multi-line text and using regular expressions

Get text between two strings

Using find() method for Getting text between two strings

The find() method helps us to locate the position of the start and end strings. Once we know the start and end position we extract the text between those positions.

We will see an example for extracting text between two strings i.e. “start” and “end”.

Python code

text = "Here is the start text and here is the end text."
start = "start"
end = "end"

#The start and end variable can hold string, character or #delimiters.
 
#Finding the positions of the start and end strings. 
start_index = text.find(start)
end_index = text.find(end)

#Now we will extract the text between
#“start” and “end” using slice operator.
 
if start_index != -1 and end_index != -1:
    extracted_text = text[start_index + len(start):end_index].strip()
    print(extracted_text)

Output

text and here is the

Using Regular Expressions to get text between two strings

When we want to extract text which has a complex pattern, we can use regular expressions (regex). Python’s re module can be used to match patterns and extract text between two strings, characters and delimiters.

Let’s take an example: Here is the input string “Start of text [Extract this part] End of text.” . In this string we will code to get the “[Extract this part]” string as output.

Python Code

import re

text = "Start of text [Extract this part] End of text."
pattern = r"Start of text \[(.*?)\] End of text"

match = re.search(pattern, text)
if match:
    extracted_text = match.group(1)
    print(extracted_text)

Output

Extract this part

Explanation of the regular expression used above example

  • Start of text \[ and \] End of text: These are the literal strings we want to match. The square brackets are escaped with backslashes because they have special meaning in regex.
  • (.*?): This is the main part of the regex that captures everything between the delimiters. The .*? matches any character (.) zero or more times (*), but in a non-greedy manner (?), so it captures the shortest match.

The search() function in the re module of python searches for the given string and if found returns a match object.

If we have more than one match, it will only return the first occurrence of the match. If no match it returns None.

Using Python, get text between two strings in multi-line text

When we are dealing with a large amount of text sometimes we want to extract text between two strings in multi line text or paragraphs.

Now lets see an example, which splits the multi line text to a list of lines using splitlines() method and we search for the “start” keyword. Once found we continue extracting text until we find the “end” keyword.

Python Code 
text = """Line 1: Here is the start
Line 2: This is the text to extract
Line 3: Here is the end of the text
Line 4: Some more text."""

start = "start"
end = "end"

# Splitting  the text into lines
lines = text.splitlines()

# Initialize flags and variables
extracting = False
extracted_text = ""

# Looping through each line from splitlines() output
for line in lines:
    if start in line:
        # Start extracting after the 'start' keyword
        extracting = True
        extracted_text += line.split(start, 1)[1].strip()  # We Start from the text after 'start'
        continue  # Skip to the next line
    if extracting:
        if end in line:
            # Stop extracting at the 'end' keyword
            extracted_text += " " + line.split(end, 1)[0].strip()  # Stop before 'end'
            break
        else:
            # Continue appending text between 'start' and 'end'
            extracted_text += " " + line.strip()


print('extracted_text:', extracted_text)
Output 
Line 2: This is the text to extract
Line 3: Here is the

Using Python, get text between two delimiters

A delimiter is a word, symbol or character which separates data for example words, lines etc. Here we are using two delimiters i.e. “start_delim” and “end_delim” , they hold values “<start>” and “<end>”.

The regex pattern uses the re.escape method which basically converts special characters to characters exactly as they appear, instead of interpreting them as special symbols with specific meanings within regular expressions. “(.*?)” This pattern captures everything in between.

Python code 
import re

def get_text_between_delimiters(text, start_delim, end_delim):
    # Regex pattern to match the text between the delimiters
    pattern = re.escape(start_delim) + "(.*?)" + re.escape(end_delim)
    
    # Find all matches
    matches = re.findall(pattern, text)
    return matches

# Example usage
text = "Here is the start delimiter <start> this is the content <end> and more text"
start_delim ="<start>" #replace value of your start delimiter
end_delim ="<end>" #replace value of end delimiter

result = get_text_between_delimiters(text, start_delim, end_delim)
print(result)
Output 
this is content

Using Python, get text between two characters

To get text between two characters we will use find() method in python. We will use the find() method twice, one for getting the first target character index and second one to get the last character index. Once we have an index to slice the string to get the necessary string.

For example I want text between these two characters : ‘[‘ , ‘]’ and text is “Hello [this is the content] world”.

Python Code

def get_text_between_chars(text, start_char, end_char):
    # Find the position of start and end characters
    start_index = text.find(start_char)
    end_index = text.find(end_char, start_index)

    # If both characters are found, return the substring between them
    if start_index != -1 and end_index != -1:
        return text[start_index + 1:end_index]
    return None  # Return None if the characters are not found

# Example usage
text = "Hello [this is the content] world"
start_char = "["
end_char = "]"

result = get_text_between_chars(text, start_char, end_char)
print(result)

Output:

this is the content

Using Python, find text between two words

Using find() method would get the index of the word we are targeting and then we will use slicing to get necessary text.

For example, I want to extract data between “start_word” and “end_word”.

Python Code

def get_text_between_words(text, start_word, end_word):
    # Find the starting position of the start_word
    start_index = text.find(start_word)
    # Find the starting position of the end_word after the start_word
    end_index = text.find(end_word, start_index)

    # If both words are found, return the text between them
    if start_index != -1 and end_index != -1:
        return text[start_index + len(start_word):end_index]
    return None  # Return None if either word is not found

# Example usage
text = "Here is the start word: start_word this is the text we want end_word and more text"
start_word = "start_word"
end_word = "end_word"

result = get_text_between_words(text, start_word, end_word)
print(result)

Output

this is content

You can also read blog on how to solve error failed building wheel for Numpy in python

Related Posts

Subscribe
Subscribe