python3 uuid to base64.urlsafe encode and decode mismatch - python-3.x

Question

I'm having a problem getting a base64-encoded uuid to match the original uuid.
Here is the code:
import base64, uuid
def uuid2slug(uuidstring):
return base64.urlsafe_b64encode(uuid.uuid1().bytes).decode("utf-8").rstrip('=\n').replace('/', '_')
def slug2uuid(slug):
return uuid.UUID(bytes=base64.urlsafe_b64decode((slug + '==').replace('_', '/')))
uid = uuid.uuid1()
urlslug = uuid2slug(uid)
urluid = slug2uuid(urlslug)
print(uid)
print(urlslug)
print(urluid)
This returns a mismatch in the uuid's first column:
cfe71fa2-7d39-11e7-9264-000c29023711
z-cg7H05EeeSZAAMKQI3EQ
cfe720ec-7d39-11e7-9264-000c29023711
Any thoughts?
This is using Python 3.5.3

Answer 1

As mentioned in the comments, the problem in your code was that you were not using the argument you passed to the function, uuidstring.
Also note that you are using the urlsafe encoding and decoding libraries, so you don't need to replace the slashes yourself.
For reference, a Base64 value can be defined with the following regex, ^[A-Za-z0-9+/]+={0,2}$, where + and - are the only non-alphanumeric symbols, and = is only used for padding. The URL encoding is explained in the Base64 (Wikipedia) article,
the '+' and '/' characters of standard Base64 are respectively replaced by '-' and '_', so that using URL encoders/decoders is no longer necessary
Long story short, the correct version of your functions, without the redundant calls to replace are:
def uuid2slug(uuidstring):
return base64.urlsafe_b64encode(uuidstring.bytes).decode("utf-8").strip('=')
def slug2uuid(slug):
return uuid.UUID(bytes=base64.urlsafe_b64decode(slug+'=='))
If you run your code a couple of times, you will find hyphens and underscores, and no slashes.
E.g.
471f8fc4-5ec5-11ed-9645-06ca5f5b4308
Rx-PxF7FEe2WRQbKX1tDCA
471f8fc4-5ec5-11ed-9645-06ca5f5b4308
ac74e9fe-5ec6-11ed-b5e7-06ca5f5b4308
rHTp_l7GEe215wbKX1tDCA
ac74e9fe-5ec6-11ed-b5e7-06ca5f5b4308