Get all the emails in a text and export it to a CSV file

convertToCSV.py

import os
import re
import csv

# Import the file
MYPATH = os.path.dirname(os.path.abspath(__file__))
FILENAME = input('The filename is : ')
INPUT_FILE = os.path.join(MYPATH, FILENAME)


def check_file(input_file):
    '''Check if file exists and creates an Object'''
    if os.path.exists(input_file):
        data = open(input_file, 'r')
        return data.read()
    else:
        print("File not found.")
        raise SystemExit


def read_file(data_read):
    '''Read & returns Emails'''
    r = re.compile(("([a-z0-9!#$%&'*+\/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+\/=?^_`"
                    "{|}~-]+)*(@|\sat\s)(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?(\.|"
                    "\sdot\s))+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?)"))
    # Reads texts and returns emails
    return r.findall(data_read)


def write_csv(emails):
    '''Write a CSV file with the emails'''
    # Define CSV
    new_filename = FILENAME[:-4]+".csv"

    # Create file
    with open(os.path.join(MYPATH, new_filename), "w") as myFile:
        writer = csv.writer(myFile)
        for email in emails:
            writer.writerow(email)
        print("Done !")


write_csv(read_file(check_file(INPUT_FILE)))