Based on XKCD-style passphrase recipe from https://docs.python.org/3/library/secrets.html#recipes-and-best-practices. Python 3.6+

gen-pass.py

#!/usr/bin/python3
"""
Based on XKCD-style passphrase recipe from
https://docs.python.org/3/library/secrets.html#recipes-and-best-practices.
"""

import secrets


TRUNCATE = 64

with open('/usr/share/dict/WORDS') as f:
    WORDS = [word.strip() for word in f]
    SEED = str(secrets.choice(range(10))).join(secrets.choice(WORDS)
                                               for i in range(12))
    LETTERS = []
    for l in SEED:
        LETTERS.append(l.upper()
                       if secrets.randbits(1) % 2 == 0
                       else l.lower())
    FINAL = ''.join(LETTERS)[::-1][:TRUNCATE]