Open a File by Regular Expression in Python

Regular expressions (regex) are powerful tools for pattern matching and manipulation of text data. When it comes to opening files based on a specific pattern or criteria, regular expressions can be a handy solution. In this article, we will explore how to open a file using regular expressions in three different programming languages: Python, JavaScript, and Ruby.

What is Regular Expression?

A regular expression, often abbreviated as “regex” or “regexp,” is a sequence of characters that defines a search pattern. It is a powerful tool used for pattern matching within strings. Regular expressions are a domain-specific language (DSL) embedded in many programming languages and tools, allowing developers to describe and match complex patterns of characters.

How to Open a File by Regular Expression?

Below, are the methods for How To Open A File By Regular Expression In Python.

Example 1: Using Basic Pattern Matching

In this example, the re.compile function is used to create a regex pattern based on the provided file_pattern. The search method is then applied to each file in the directory, and matching files are opened and their content is printed.

Python3

import re

def open_file_by_regex(file_pattern):
    # List all files in the current directory
    files = ["example.txt", "data.csv", "report.docx", "image.png"]

    # Use regex to match files based on the provided pattern
    pattern = re.compile(file_pattern)
    matching_files = [file for file in files if pattern.search(file)]

    # Open and print the content of each matching file
    for file_name in matching_files:
        with open(file_name, 'r') as file:
            content = file.read()
            print(f"Content of {file_name}:\n{content}\n")

# Example usage
open_file_by_regex(r'.*\.txt')

Output

Content of example.txt:
Hello GeeksforGeeks

Example 2 : Extracting Information from File Name

In this example, the regex pattern includes groups ((\d{4})(\d{2})(\d{2})) to extract year, month, and day from file names containing timestamps. The extracted information is then printed alongside the file name.

Python3

import re

def open_file_by_regex_and_extract(file_pattern):
    # List all files with timestamps in their names
    files = ["20220101_report.txt", "20220215_data.csv", "20220320_summary.docx"]

    # Use regex groups to extract relevant information
    pattern = re.compile(r'(\d{4})(\d{2})(\d{2})_' + file_pattern)
    for file_name in files:
        match = pattern.match(file_name)
        if match:
            year, month, day = match.groups()
            print(f"Date: {year}-{month}-{day}, File: {file_name}")

# Example usage
open_file_by_regex_and_extract(r'.*\.txt')

Output

Date: 2022-01-01, File: 20220101_report.txt:
Hi, GeeksforGeeks

Conclusion

In conclusion, leveraging regular expressions in Python to open files provides a versatile and dynamic approach for handling specific patterns within file names. The presented code examples demonstrate the flexibility of regular expressions in matching and extracting relevant information from file names. Whether conducting basic pattern matching, extracting data from timestamps, or performing case-insensitive searches, regular expressions empower users to streamline file-handling processes.