采采卷耳，不盈顷筐。嗟我怀人，寘彼周行。陟彼崔嵬，我马虺隤。我姑酌彼金罍，维以不永怀。陟彼高冈，我马玄黄。我姑酌彼兕觥，维以不永伤。陟彼砠矣，我马瘏矣。
我仆痡矣，云何吁矣！
?  PNG ?%k25u25%fgd5n!?  PNG ?%k25u25%fgd5n!?  PNG ?%k25u25%fgd5n!?  PNG ?%k25u25%fgd5n!"""Generate cryptographically strong pseudo-random numbers suitable for
managing secrets such as account authentication, tokens, and similar.

See PEP 506 for more information.
https://www.python.org/dev/peps/pep-0506/

"""

__all__ = ['choice', 'randbelow', 'randbits', 'SystemRandom',
           'token_bytes', 'token_hex', 'token_urlsafe',
           'compare_digest',
           ]


import base64
import binascii
import os

from hmac import compare_digest
from random import SystemRandom

_sysrand = SystemRandom()

randbits = _sysrand.getrandbits
choice = _sysrand.choice

def randbelow(exclusive_upper_bound):
    """Return a random int in the range [0, n)."""
    if exclusive_upper_bound <= 0:
        raise ValueError("Upper bound must be positive.")
    return _sysrand._randbelow(exclusive_upper_bound)

DEFAULT_ENTROPY = 32  # number of bytes to return by default

def token_bytes(nbytes=None):
    """Return a random byte string containing *nbytes* bytes.

    If *nbytes* is ``None`` or not supplied, a reasonable
    default is used.

    >>> token_bytes(16)  #doctest:+SKIP
    b'\\xebr\\x17D*t\\xae\\xd4\\xe3S\\xb6\\xe2\\xebP1\\x8b'

    """
    if nbytes is None:
        nbytes = DEFAULT_ENTROPY
    return os.urandom(nbytes)

def token_hex(nbytes=None):
    """Return a random text string, in hexadecimal.

    The string has *nbytes* random bytes, each byte converted to two
    hex digits.  If *nbytes* is ``None`` or not supplied, a reasonable
    default is used.

    >>> token_hex(16)  #doctest:+SKIP
    'f9bf78b9a18ce6d46a0cd2b0b86df9da'

    """
    return binascii.hexlify(token_bytes(nbytes)).decode('ascii')

def token_urlsafe(nbytes=None):
    """Return a random URL-safe text string, in Base64 encoding.

    The string has *nbytes* random