Simple lexer and parser for a calculator in python. You can use the same logic to create your own programming language

calculate-lang.py

tokens = ["+", "-", "/", "*", "^"]


def parse(source):
    characters = list(source)
    final = []
    for char in characters:
        if char.isdigit():
            final.append(float(char))
        else:
            for token in tokens:
                if char == token:
                    final.append(token)
                    break
            else:
                raise SyntaxError("Invalid character '" + char + "'")
    return final


def evaluate(parsed):
    stack = []
    for item in parsed:
        if isinstance(item, float) or (isinstance(item, str) and item.isdigit()):
            stack.append(float(item))
        else:
            stack.append(item)

    # Initialize the result with the first number in the stack
    result = stack[0]

    for i in range(1, len(stack), 2):
        operator = stack[i]
        operand = stack[i + 1]
        if operator == "+":
            result += operand
        elif operator == "-":
            result -= operand
        elif operator == "/":
            result /= operand
        elif operator == "*":
            result *= operand
        elif operator == "^":
            result **= operand

    print(result)


while True:
    source = input("> ")
    if not source:
        break
    try:
        parsed = parse(source)
        evaluate(parsed)
    except SyntaxError as e:
        print("Syntax Error: " + str(e))
    except IndexError as e:
        print("Index Error: " + str(e))
    except ValueError as e:
        print("Value Error: " + str(e))

The code has an operator precedence problem.

The code has an operator precedence problem.

@luisespino it was a simple test to showcase a tokenizer