Python: Reversibly encode alphanumeric string to integer

Question

I want to convert a string (composed of alphanumeric characters) into an integer and then convert this integer back into a string:

string --> int --> string

In other words, I want to represent an alphanumeric string by an integer.

I found a working solution, which I included in the answer, but I do not think it is the best solution, and I am interested in other ideas/methods.

Please don't tag this as duplicate just because a lot of similar questions already exist, I specifically want an easy way of transforming a string into an integer and vice versa.

This should work for strings that contain alphanumeric characters, i.e. strings containing numbers and letters.

Answer 1

Here's what I have so far:

string --> bytes

mBytes = m.encode("utf-8")

bytes --> int

mInt = int.from_bytes(mBytes, byteorder="big")

int --> bytes

mBytes = mInt.to_bytes(((mInt.bit_length() + 7) // 8), byteorder="big")

bytes --> string

m = mBytes.decode("utf-8")

try it out:

m = "test123"
mBytes = m.encode("utf-8")
mInt = int.from_bytes(mBytes, byteorder="big")
mBytes2 = mInt.to_bytes(((mInt.bit_length() + 7) // 8), byteorder="big")
m2 = mBytes2.decode("utf-8")
print(m == m2)

---

Here is an identical reusable version of the above:

class BytesIntEncoder:

    @staticmethod
    def encode(b: bytes) -> int:
        return int.from_bytes(b, byteorder='big')

    @staticmethod
    def decode(i: int) -> bytes:
        return i.to_bytes(((i.bit_length() + 7) // 8), byteorder='big')

If you're using Python <3.6, remove the optional type annotations.

Test:

>>> s = 'Test123'
>>> b = s.encode()
>>> b
b'Test123'

>>> BytesIntEncoder.encode(b)
23755444588720691
>>> BytesIntEncoder.decode(_)
b'Test123'
>>> _.decode()
'Test123'

Answer 2

Recall that a string can be encoded to bytes, which can then be encoded to an integer. The encodings can then be reversed to get the bytes followed by the original string.

This encoder uses binascii to produce an identical integer encoding to the one in the answer by charel-f. I believe it to be identical because I extensively tested it.

Credit: this answer.

from binascii import hexlify, unhexlify

class BytesIntEncoder:

    @staticmethod
    def encode(b: bytes) -> int:
        return int(hexlify(b), 16) if b != b'' else 0

    @staticmethod
    def decode(i: int) -> int:
        return unhexlify('%x' % i) if i != 0 else b''

If you're using Python <3.6, remove the optional type annotations.

Quick test:

>>> s = 'Test123'
>>> b = s.encode()
>>> b
b'Test123'

>>> BytesIntEncoder.encode(b)
23755444588720691
>>> BytesIntEncoder.decode(_)
b'Test123'
>>> _.decode()
'Test123'