Password Generator

#!/usr/bin/python
# -*- coding: utf-8 -*-
# Author: Covey

import itertools
import argparse
import sys
import re

# Variables to get data from command line arguments
filename = 'data.txt'   # Default value
count = 3;              # Default value
substitute = False      # Default value

# Reads data from file into list. Throws exception if something fails
try:
    global datalist
    datalist = open(filename,'r').readlines()
    datalist = [i.strip() for i in datalist] + [i.lower().strip() for i in datalist]
except:
    print('\nNo datafile found! Exiting...')
    sys.exit(1)

# Adds optional arguments to the program
parser = argparse.ArgumentParser()
parser.add_argument('-c', '--count', help='Number of words to combine the passwordlist into', type=int)
parser.add_argument('-s', '--substitute', help='Substitute known letter/integer combinations and add to passwordlist', action='store_true')
parser.add_argument('-f', '--file', help='Specify path to datafile')
parser.add_argument('-q','--quick', help='Setting this will write each password directly to the output file without any formating or checks. (Strange things may occur in output file)', action='store_true')

# This function gets called if the '-q | --quick' argument is set. It will combine all the words contained
# in the datafile to a maximum of 'count' words, and write each password directly to the output file without
# any formatting or checks. This may lead to strange output and duplicate listings.
def generateQuick():
    try:
        file = open(filename, 'w')
        [file.write(''.join(j)) for i in range(1, count + 1) for j in itertools.permutations(datalist, i)]
        file.close()
        print('Passwords generated and written to file!')
    except:
        print('\nFailed to write to file! Exiting...')
        sys.exit(1)

# This function combines all the words contained in datafile into a passwordlist with all possible
# combinations, no repeated elements, and a maximum length of 'count' words.
def generateNormal():
    global pwlist
    pwlist = [''.join(j) for i in range(1, count + 1) for j in itertools.permutations(datalist, i)]
    print('Passwords generated!')

# If argument set, replacing letters with look-alike integers.
# NB! Using regular expressions like this may produce duplicate values
def substitute():
    global pwlist
    # Substitutes 'i' and 'I' with the number 1
    pwlist += [re.sub('(i)|(I)', '1', i) for i in pwlist]
    # Substitutes 'a' and 'A' with the number 4
    pwlist += [re.sub('(a)|(A)', '4', i) for i in pwlist]
    # Substitutes 'o' and 'O' with the number 0
    pwlist += [re.sub('(o)|(O)', '0', i) for i in pwlist]
    # Substitutes 'e' and 'E' with the number 3
    pwlist += [re.sub('(e)|(E)', '3', i) for i in pwlist]
    # Substitutes 't' and 'T' with the number 7
    pwlist += [re.sub('(t)|(T)', '7', i) for i in pwlist]
    # Substitutes 's' and 'S' with the number 5
    pwlist += [re.sub('(s)|(S)', '5', i) for i in pwlist]
    # Substitutes 's' and 'S' with the symbol $
    pwlist += [re.sub('(s)|(S)', '$', i) for i in pwlist]
    # Substitutes 'l' and 'L' with the symbol £
    pwlist += [re.sub('(l)|(L)', '£', i) for i in pwlist]
    # Substitutes 'a' and 'A' with the symbol @
    pwlist += [re.sub('(a)|(A)', '@', i) for i in pwlist]
    # Substitutes 'b' with the number 6
    pwlist += [re.sub('b', '6', i) for i in pwlist]

def formatPasswords():
    global pwlist
    # Removes duplicates present in the list
    pwlist = list(set(pwlist))

def writeToFile():
    global pwlist
    try:
        # Generates the file containing the passwords, over-writing old file if present
        file = open('password_list.txt', 'w')
        [file.write(i + "\n") for i in pwlist]
        file.close()
        print('Passwords written to file!')
    except:
        print('Failed to write into file! Exiting...')
        sys.exit(1)

# Check to see if any arguments are present at runtime
args = parser.parse_args()
if args.count:
    # Set the number of words to be combined from the datafile
    count = args.c
if args.substitute:
    # Turns on substitution of look-alike chars
    substitute = True
if args.file:
    # Uses custom path to datafile
    filename = args.f
if args.quick:
    generateQuick()
    sys.exit(0)
else:
    generateNormal()
    if substitute:
        substitute()
    formatPasswords()
    writeToFile()
    sys.exit(0)