partTwo.py

import re


def is_number(str):
    try:
        int(str)
        return True
    except ValueError:
        return False


def is_name(str):
    return re.match("\w+", str)


def peek(stack):
    return stack[-1] if stack else None


def apply_operator(operators, values):
    operator = operators.pop()
    right = values.pop()
    left = values.pop()
    values.append(eval("{0}{1}{2}".format(left, operator, right)))


def greater_precedence(op1, op2):
    precedences = {"+": 2, "-": 0, "*": 1, "/": 1}
    return precedences[op1] > precedences[op2]


def evaluate(expression):
    tokens = re.findall("[+/*()-]|\d+", expression)
    values = []
    operators = []
    for token in tokens:
        if is_number(token):
            values.append(int(token))
        elif token == "(":
            operators.append(token)
        elif token == ")":
            top = peek(operators)
            while top is not None and top != "(":
                apply_operator(operators, values)
                top = peek(operators)
            operators.pop()  # Discard the '('
        else:
            # Operator
            top = peek(operators)
            while (
                top is not None and top not in "()" and greater_precedence(top, token)
            ):
                apply_operator(operators, values)
                top = peek(operators)
            operators.append(token)
    while peek(operators) is not None:
        apply_operator(operators, values)

    return values[0]


def partTwo(instr: str) -> int:
    expressions = instr.strip().split("\n")

    sigma = 0

    for expression in expressions:
        sigma += evaluate(expression)

    return sigma