lisp_parser.py

lisp = input("Enter your Lisp code: ")

# splits Lisp expression into tokens and strips them of whitespace.
def makeTokens(lisp):
    lispTokens = lisp.replace("(", " ( ").replace(")", " ) ").split()
    return [token.strip() for token in lispTokens]

# if the token is a number, return it as the appropriate type (int or float).
# otherwise, return it as a string
def createAtom(token):
    try:
        return int(token)
    except:
        try:
            return float(token)
        except:
            return str(token)

def makeAST(lispTokens):
    if len(lispTokens) == 0:
        return "You need to have some text!"
    currentToken = lispTokens.pop(0)
    if currentToken == "(": # beginning of a new expression
        newExpressionList = []
        while lispTokens[0] != ")": # put everything in the form into a list
            newExpressionList.append(makeAST(lispTokens))
        lispTokens.pop(0)
        return newExpressionList
    else: # if the token is an atom, return the atom
        return createAtom(currentToken)

tokens = makeTokens(lisp)
ast = makeAST(tokens)

print(ast)