如何从 2 个字符串生成唯一键？

Question

Let's say I have "username1" and "username2"

How can I combine these two usernames together to generate a unique value?

The value should be the same no matter how they are combined if username2 is entered first or vice versa the two names should always combine to become the same unique value. The string length will not work as other usernames can have the same length.

Is there a simple way to do this or a technique for this?

Answer 1

Sets are unordered, and Python has a hashable immutable set type, assuming your requirement for a unique key is that it can be used as a dict key:

def key(a, b):
    return frozenset([a, b])

d = {}
d[key("foo", "bar")] = "baz"
print(d[key("bar", "foo")])

You can also create a sorted tuple:

def key(a, b):
    return tuple(sorted([a, b]))

d = {}
d[key("foo", "bar")] = "baz"
print(d[key("bar", "foo")])

Answer 2

There are many ways to generate a unique value. One common (to sysops) method is the one used to get a UNIX UUID (Universally Unique IDentifier) from the routines supplied with most major languages. In case of parsing problems, use a separator that does not appear in your input strings.

If you replace my constant strings "username1" and "username2" with your variables, I believe that your problem is solved.

import uuid
unique_sep = '|'    # I posit vertical bar as not appearing in any user name

import uuid
unique_ID = uuid.uuid5(uuid.NAMESPACE_X500, "username1" + unique_sep + "username2")
print(unique_ID)

Output:

b2106742-94f5-596d-a461-c977b5982d85

To preserve uniqueness from entry order, simply sort them in any convenient fashion, such as:

names_in = [username1, username2]
unique_ID = uuid.uuid5(uuid.NAMESPACE_X500, min(names_in) + unique_sep + max(names_in))