In this blog post, we’ll learn how to extract a specific portion of text between two substrings in a given input string. This technique is useful in various scenarios, such as processing file paths, extracting data from logs, or handling any structured text data.

Problem Statement

Given a string, we want to extract the part of the text that is between two specified substrings, excluding the ending substring. For example, from the following path:

C:\\Example\\Projects\\DataProcessing\\user\\tasks\\_STTM\\Logs\\Account Data Logs\\Transaction_Details_Report.sql

we want to extract the part between \\Logs and .sql, which should result in:

Account Data Logs\\Transaction_Details_Report

Solution

We’ll use Python’s re module, which provides support for regular expressions, to achieve this. Regular expressions offer a powerful way to search for and manipulate text patterns.

Step-by-Step Guide

1. Import the re Module: This module provides functions to work with regular expressions.
2. Define the Function: Create a function that takes the input text, start string, and end string as arguments.
3. Build the Regular Expression Pattern: Construct a pattern that matches the text between the start and end strings.
4. Search for the Pattern: Use the re.search function to find the match.
5. Extract the Desired Text: If a match is found, extract and return the text between the start and end strings.

Here’s the Python code to accomplish this:

import re

def extract_text_between_strings(input_text, start_string, end_string):
    # Create the regular expression pattern
    pattern = re.escape(start_string) + "(.*?)" + re.escape(end_string)
    
    # Search for the pattern in the input text
    match = re.search(pattern, input_text)
    
    # If a match is found, return the extracted text
    if match:
        return match.group(1)
    else:
        return None

# Example usage
input_text = "C:\\Example\\Projects\\DataProcessing\\user\\tasks\\_STTM\\Logs\\Account Data Logs\\Transaction_Details_Report.sql"
start_string = "\\Logs"
end_string = ".sql"

# Extract the text between the specified substrings
result = extract_text_between_strings(input_text, start_string, end_string)

print(result)  # Output: Account Data Logs\Transaction_Details_Report

Explanation

• re.escape(start_string) and re.escape(end_string): These functions escape any special characters in the start and end strings to ensure they are treated as literal text in the pattern.
• (.*?): This non-greedy match captures any text between the start and end strings without including them.

Conclusion

By using regular expressions in Python, you can efficiently extract specific parts of text between two substrings. This method is versatile and can be applied to various text-processing tasks. Experiment with different input strings and patterns to fully understand the power of regular expressions.