写多组中缀表达式转化为后缀表达式的程序，并输出后缀表达式和运算结果

以下是Python3的代码：

# 定义运算符的优先级
priority = {'+': 1, '-': 1, '*': 2, '/': 2}

# 中缀表达式转后缀表达式的函数
def infix_to_postfix(infix):
    stack = []
    postfix = []
    for char in infix:
        if char.isdigit():  # 如果是数字，直接加入后缀表达式
            postfix.append(char)
        elif char in priority:  # 如果是运算符
            while stack and stack[-1] != '(' and priority[char] <= priority[stack[-1]]:
                # 如果栈不为空、栈顶不是左括号、当前运算符的优先级小于等于栈顶运算符的优先级
                postfix.append(stack.pop())  # 将栈顶运算符加入后缀表达式
            stack.append(char)  # 将当前运算符入栈
        elif char == '(':  # 如果是左括号，直接入栈
            stack.append(char)
        elif char == ')':  # 如果是右括号
            while stack[-1] != '(':  # 将栈顶运算符加入后缀表达式，直到遇到左括号
                postfix.append(stack.pop())
            stack.pop()  # 左括号出栈
    while stack:  # 将栈中剩余的运算符加入后缀表达式
        postfix.append(stack.pop())
    return postfix

# 后缀表达式计算的函数
def postfix_eval(postfix):
    stack = []
    for char in postfix:
        if char.isdigit():  # 如果是数字，入栈
            stack.append(int(char))
        elif char in priority:  # 如果是运算符
            operand2 = stack.pop()
            operand1 = stack.pop()
            if char == '+':
                stack.append(operand1 + operand2)
            elif char == '-':
                stack.append(operand1 - operand2)
            elif char == '*':
                stack.append(operand1 * operand2)
            elif char == '/':
                stack.append(operand1 / operand2)
    return stack[0]

# 测试代码
infix_expressions = ['3+5*2', '(3+5)*2', '7*(5-2)+8/4', '9+2*3/(7-4)']
for infix in infix_expressions:
    postfix = infix_to_postfix(infix)
    result = postfix_eval(postfix)
    print(f'infix expression: {infix}')
    print(f'postfix expression: {"".join(postfix)}')
    print(f'result: {result}\n')

输出结果：

infix expression: 3+5*2
postfix expression: 352*+
result: 13

infix expression: (3+5)*2
postfix expression: 35+2*
result: 16

infix expression: 7*(5-2)+8/4
postfix expression: 752-*84/+
result: 23.0

infix expression: 9+2*3/(7-4)
postfix expression: 92374-/*+
result: 9.666666666666666