简单的 Python 带括号四则运算计算器 / Simple Python elementary arithmetic calculator

calculator.py

def merge(ops: list[str], values: list[int], final_merger=False):
    priority = {'*': 1, '/': 1, '+': 2, '-': 2, '$': 9999}
    while True:
        if len(ops) >= 2:
            last, last_last = [ops.pop() for _ in range(2)]
            if final_merger:
                last_last, last = last, last_last
        elif len(ops) >= 1 and len(values) >= 2:
            last_last, last = ops.pop(), '$'
        else:
            break

        if priority[last_last] <= priority[last] or final_merger:
            right, left = values.pop(), values.pop()
            values.append(eval(f'{left} {last_last} {right}'))
            last != '$' and ops.append(last)
        else:
            ops.append(last_last)
            last != '$' and ops.append(last)
            break


def less_eval(exp: str) -> tuple[list[str], list[int], str]:
    values = []
    ops = []
    i = 0
    waiting_next_number = False
    while i < len(exp):
        char = exp[i]
        if char in '0123456789':
            value = int(char)
            while i+1 < len(exp) and (new_char := exp[i+1]) in '0123456789':
                value = value * 10 + int(new_char)
                i += 1
            values.append(value)
        elif char in '+-*/':
            ops.append(char)
            merge(ops, values)
        elif char == '(':
            new_ops, new_values, new_exp = less_eval(exp[i + 1:])
            values.append(new_values[0])
            i += len(new_exp) + 1
        elif char == ')':
            merge(ops, values, final_merger=True)
            return ops, values, exp[:i]
        waiting_next_number = False if waiting_next_number else True
        i += 1
    merge(ops, values, final_merger=True)
    return ops, values, exp[:i]


def test_less_eval():
    assert less_eval('0 - 2')[:2] == ([], [-2])
    assert less_eval('2 * 2')[:2] == ([], [4])
    assert less_eval('2 / 2')[:2] == ([], [1])
    assert less_eval('20 / 2')[:2] == ([], [10])
    assert less_eval('20 / 20')[:2] == ([], [1])
    assert less_eval('20 / 200')[:2] == ([], [0.1])

    assert less_eval('(1 + 2) * 3')[:2] == ([], [9])
    assert less_eval('(1 + 2) * 3 + 2 / 2')[:2] == ([], [10])
    assert less_eval('(1 + 2) * (3 + 2 * (2 + 1)) / 2')[:2] == ([], [13.5])
    assert less_eval('0 - 2 -3 - 4 -5   ')[:2] == ([], [-14])

    assert less_eval('1 + 2 * 3')[:2] == ([], [7])
    assert less_eval('(1 + 2) * (3 + 2 * (2 + 1 + 1)) / 2')[:2] == ([], [16.5])


def test_with_random():
    from time import time
    import random

    for i in range(100):
        new_exp = []
        while len(new_exp) < 50:
            new_exp.append(random.choice('123456789'))
            new_exp.append(random.choice('+-*/'))
        new_exp.append(random.choice('123456789'))
        for j in range(random.randint(5, 15)):
            left_index = random.randint(0, len(new_exp) - 3)
            while new_exp[left_index] not in '0123456789':
                left_index = random.randint(0, len(new_exp) - 3)
            new_exp.insert(left_index, '(')

            right_index = random.randint(left_index, len(new_exp) - 1)
            while new_exp[right_index] not in '0123456789':
                right_index = random.randint(left_index + 1, len(new_exp) - 1)
            new_exp.insert(right_index + 1, ')')
        try:
            exp = "".join(new_exp)
            t = time()
            v1 = eval(exp)
            t1 = time() - t

            v2 = less_eval(exp)[1][0]
            t2 = time() - (t + t1)
            assert v1 == v2
            print(t1, t2)
        except ZeroDivisionError:
            print(exp, 'ZeroDivisionError')