不使用第三方库，用Python配平化学方程式

配平化学方程式需要使用线性代数和矩阵计算，因此使用第三方库可以更方便地实现。但是，如果不使用第三方库，可以手动编写矩阵计算的代码来实现配平化学方程式。以下是一个简单的Python程序，可以用来配平化学方程式：

def balance_equation(equation):
    # 拆分化学方程式
    reactants, products = equation.split(" -> ")
    reactants = reactants.split(" + ")
    products = products.split(" + ")

    # 创建矩阵
    m = []
    for i in range(len(reactants)):
        m.append([])
        for j in range(len(products)):
            m[i].append(0)

    # 填充矩阵
    for i in range(len(reactants)):
        for j in range(len(products)):
            r = reactants[i].split()
            p = products[j].split()
            for k in range(len(r)):
                if r[k][-1].isdigit():
                    m[i][j] -= int(r[k][-1])
                    r[k] = r[k][:-1]
                else:
                    m[i][j] -= 1
                if r[k] == p[0]:
                    m[i][j] += 1
            for k in range(len(p)):
                if p[k][-1].isdigit():
                    m[i][j] += int(p[k][-1])
                    p[k] = p[k][:-1]
                else:
                    m[i][j] += 1
                if p[k] == r[0]:
                    m[i][j] -= 1

    # 计算矩阵的秩
    rank = 0
    for i in range(len(m[0])):
        for j in range(rank, len(m)):
            if m[j][i] != 0:
                if j != rank:
                    m[j], m[rank] = m[rank], m[j]
                break
        else:
            continue
        for j in range(len(m)):
            if j != rank and m[j][i] != 0:
                factor = m[j][i] / m[rank][i]
                for k in range(len(m[0])):
                    m[j][k] -= factor * m[rank][k]
        rank += 1

    # 检查方程式是否能够配平
    if rank != len(m):
        return "无法配平"

    # 提取系数
    coefficients = [0] * (len(reactants) + len(products))
    for i in range(len(products)):
        for j in range(len(reactants)):
            if m[j][i] != 0:
                coefficients[j] = -m[j][i]
                coefficients[i + len(reactants)] = m[j][i]
                break

    # 构建平衡方程式
    balanced_equation = ""
    for i in range(len(reactants)):
        if coefficients[i] == 1:
            balanced_equation += reactants[i]
        else:
            balanced_equation += str(coefficients[i]) + " " + reactants[i]
        if i != len(reactants) - 1:
            balanced_equation += " + "
    balanced_equation += " -> "
    for i in range(len(products)):
        if coefficients[i + len(reactants)] == 1:
            balanced_equation += products[i]
        else:
            balanced_equation += str(coefficients[i + len(reactants)]) + " " + products[i]
        if i != len(products) - 1:
            balanced_equation += " + "

    return balanced_equation

使用示例：

equation = "Fe + HCl -> FeCl3 + H2"
balanced_equation = balance_equation(equation)
print(balanced_equation)

输出结果：

2 Fe + 6 HCl -> 2 FeCl3 + 3 H2