此模块提供不可变的 UUID 对象 (类 uuid) 和函数uuid1()、uuid3()、uuid4()、uuid5(),
用于生成在 RFC 4122 中指定版本1、3、4和5UUIDs 。如果你想要的只是一个唯一
的ID，你应该调用uuid1()或uuid4()。请注意, uuid1()可能会损害隐私, 因为它创建了一
个 UUID, 其中包含计算机的网络地址。
典型用法：
>>> import uuid
# make a UUID based on the host ID and current time
>>> uuid.uuid1() # doctest: +SKIP
UUID('a8098c1a-f86e-11da-bd1a-00112444be1e')
# make a UUID using an MD5 hash of a namespace UUID and a name
>>> uuid.uuid3(uuid.NAMESPACE_DNS, 'python.org')
UUID('6fa459ea-ee8a-3ca4-894e-db77e160355e')
# make a random UUID
>>> uuid.uuid4() # doctest: +SKIP
UUID('16fd2706-8baf-433b-82eb-8c7fada847da')
# make a UUID using a SHA-1 hash of a namespace UUID and a name
>>> uuid.uuid5(uuid.NAMESPACE_DNS, 'python.org')
UUID('886313e1-3b8a-5372-9b90-0c9aee199e5d')
# make a UUID from a string of hex digits (braces and hyphens ignored)
>>> x = uuid.UUID('{00010203-0405-0607-0809-0a0b0c0d0e0f}')
# convert a UUID to a string of hex digits in standard form
>>> str(x)
'00010203-0405-0607-0809-0a0b0c0d0e0f'
# get the raw 16 bytes of the UUID
>>> x.bytes
b'\x00\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\r\x0e\x0f'
# make a UUID from a 16-byte string
>>> uuid.UUID(bytes=x.bytes)
UUID('00010203-0405-0607-0809-0a0b0c0d0e0f')来源：https://github.com/python/cpython/blob/3.7/Lib/uuid.py
