#! python3

#   `regexSearch`: Finds all lines matching a given regex in each file in a given folder.

#   Usage:

#       The directory to search and regex to be searched for are provided as a command line arguments.

#       The 1st and 2nd command line arguments are the directory and regex pattern respectively.

#       Script prompts the user to enter the regex.

#       After completion, the user is prompted to continue



import re, sys

from os import path, listdir



def regex_search(regex, directory):

    res, lst = {}, listdir(directory)

    for itm in lst:

        pth = path.join(path.abspath(directory), itm)

        if path.isdir(pth):   res.update(regex_search(regex, pth))    #Recursively traverse all sub directories.

        else:

            print(pth)

            with open(pth) as file:  

                tmp = []

                for idx, line in enumerate(file.readlines()):

                    results = regex.findall(line)

                    if results:  tmp.extend([f"Line {idx+1}: {results}"])

                res[pth] = tmp

    return res



if __name__ == "__main__":

    directory, pattern = sys.argv[1:3]

    while not path.isdir(directory):

        print("Error: Please input a valid path for an existing directory:", end = "t")

        directory = input()

    while True:

        try:

            regex = re.compile(pattern)

            break

        except TypeError:

            print("Error: Please input a valid regex:", end = "t")

            pattern = input()

        except re.error:

            print("Error: Please input a valid regex:", end = "t")

            pattern = input()

    matches = regex_search(regex, directory)

    for key in matches:  print(key, "n".join(matches[key]), sep="n", end="nn")

Some improvements

• 
  

  Style

  
  
  

  Please indent your file properly, since indentation is important in Python, those lines like

  
  
  

  
  

  if path.isdir(pth):   res.update(regex_search(regex, pth))
  
  

  
  

  
  
  

  Are frowned upon, instead do

  
  
  

  if path.isdir(pth):
  
      res.update(regex_search(regex, pth))
  
  

  
  


• 
  

  Use glob for listing files in a directory

  
  
  

  With Python3.5+ glob is the easiest way to list all files in a directory and subdirectory, before you should use os.walk()

  
  


• 
  

  Use generators when appropriate

  
  
  

  This will save some memory space, as it doesn't have to append to the temporary list all the time

  
  


• 
  

  Use argparse over sys.argv[]

  
  
  

  Argparse is the module for CLI input, easy to use and has a ton of features I definitely recommend it!

  
  

Code

import argparse

import glob

import re

import os

import pathlib



def regex_search(regex, directory):

    for f in glob.glob(f"{directory}**/*.*", recursive=True):

        with open(f) as _file:

            for i, line in enumerate(_file.readlines()):

                if regex.search(line):

                    yield f"In file {f} matched: {line.rstrip()} at position: {i}"



def parse_args():

    parser = argparse.ArgumentParser(

        usage='%(prog)s [options] <regex> <directory>',

        formatter_class=argparse.RawDescriptionHelpFormatter

    )

    parser.add_argument('regex', type=str)

    parser.add_argument('directory', type=str)

    args = parser.parse_args()



    try:

        rgx = re.compile(args.regex)

    except Exception as e:

        parser.error('Regex does not compile')

    directory = pathlib.Path(args.directory)

    if not os.path.isdir(directory):

        parser.error('Directory is not valid')

    return rgx, directory



if __name__ == '__main__':

    regex, directory = parse_args()

    for match in regex_search(regex, directory):

        print(match)

Bonus Round!

grep is a Unix tool that can basically do this by default

grep -Hrn 'search term' path/to/dir

Where:

• 
  -H prints the matching line


• 
  -r Does a recursive search


• 
  -n prints the line number