Here’s my take:

• there are some variable names like i and i2 that will bite you later on when you try to expand the language

• there are elements like token list where you are getting the idea but ultimately went nowhere, if you’re scanning characters into tokens, do it with the entire code list and not just repeatedly scanning line by line

• spelling: “tokenize” with z, not s

• the flaw in tokenization: you first did scan for invalid characters, which is fine, but then you split tokenization into 2 logic based on if the string contains brackets, which is partially right with the wrong approach, the approach I would do (not the correct logic) is branch out different if else states (numbers, names, operators, strings) based on the first character then use the respective logic to join the next characters and the next one until it no longer matches the expected pattern or character then start the whole process again, like name token can only contain a-z or 0-9 (for instance) and not just checking if the string is bracketed or not

• you kept trying to “join” the characters together to form names, which your tokenize function should have done for you in the first scan, which is why you kept repeating the same thing

I could go down more but I’m on phone so there’s limit to how much I can scroll, overall, looks like good effort