generate secure Django SECRE_KEY

secret_key_gen.py

"""
Two things are wrong with Django's default `SECRET_KEY` system:

1. It is not random but pseudo-random
2. It saves and displays the SECRET_KEY in `settings.py`

This snippet
1. uses `SystemRandom()` instead to generate a random key
2. saves a local `secret.txt`

The result is a random and safely hidden `SECRET_KEY`.
"""
import os
try:
    SECRET_KEY
except NameError:
    SECRET_FILE = os.path.join('secret.txt')
    try:
        SECRET_KEY = open(SECRET_FILE).read().strip()
    except IOError:
        try:
            import random
            SECRET_KEY = ''.join([random.SystemRandom().choice('abcdefghijklmnopqrstuvwxyz0123456789!@#$%^&*(-_=+)') for i in range(50)])
            secret = file(SECRET_FILE, 'w')
            secret.write(SECRET_KEY)
            secret.close()
        except IOError:
            Exception('Please create a %s file with random characters \
            to generate your secret key!' % SECRET_FILE)