def uuid4():
    """Generate a random UUID."""
    # When the system provides a version-4 UUID generator, use it.
    if _uuid_generate_random:
        _buffer = ctypes.create_string_buffer(16)
        _uuid_generate_random(_buffer)
        return UUID(bytes=_buffer.raw)
    # Otherwise, get randomness from urandom or the 'random' module.
    try:
        import os
        return UUID(bytes=os.urandom(16), version=4)
    except:
        import random
        bytes = [chr(random.randrange(256)) for i in range(16)]
        return UUID(bytes=bytes, version=4)

import string
import random
 
 
class _A(object):
	def __init__(self, name, hash_code):
		self.name = name
		self.hash_code = hash_code
 
 
class A(object):
	current_hashes = set()
 
	@classmethod
	def generate_hash_code(cls):
		while True:
			hash_code = ''.join([random.choice(string.ascii_uppercase + string.ascii_lowercase + string.digits) for _ in range(random.randint(10, 15))])
			if hash_code not in cls.current_hashes:
				cls.current_hashes.add(hash_code)
				return hash_code
 
	def __new__(cls, *args, **kwargs):
		hash_code = cls.generate_hash_code()
		kwargs.update({'hash_code': hash_code})
		return _A(*args, **kwargs)
 
 
print A('Test').hash_code
print A('Test').hash_code
print A('Test').hash_code
print A('Test').hash_code
print A('Test').hash_code
print 'Current hashes:', A.current_hashes

hdPhslOit2uRCZ
OJiLbln6dl8Ru
R4ghafikMex94
ktmsfG3yRD
VIflbXYnvqw4RC
Current hashes: set(['ktmsfG3yRD', 'VIflbXYnvqw4RC', 'OJiLbln6dl8Ru', 'R4ghafikMex94', 'hdPhslOit2uRCZ'])