如何找到括号并计算化学成分中元素的百分比？

import re

# 元素周期表中的原子质量
atomic_mass = {
    'H': 1.008, 'He': 4.003, 'Li': 6.941, 'Be': 9.012, 'B': 10.811,
    'C': 12.011, 'N': 14.007, 'O': 15.999, 'F': 18.998, 'Ne': 20.180,
    # 其他元素...
}

def parse_chemical_formula(formula):
    # 使用正则表达式找到所有元素及其数量
    elements = re.findall(r'([A-Z][a-z]*)(\d*)', formula)
    return elements

def calculate_percentage(elements, formula_mass):
    percentages = {}
    for element, count in elements:
        if count == '':
            count = 1
        else:
            count = int(count)
        mass = atomic_mass[element] * count
        percentages[element] = (mass / formula_mass) * 100
    return percentages

# 示例化学式
formula = "H2O"
elements = parse_chemical_formula(formula)

# 计算分子量
formula_mass = sum(atomic_mass[element] * int(count) if count != '' else atomic_mass[element] for element, count in elements)

# 计算元素百分比
percentages = calculate_percentage(elements, formula_mass)
print(percentages)