python实现逆波兰计算表达式的代码

如下资料是关于python实现逆波兰计算表达式的代码。

成都创新互联公司服务项目包括云浮网站建设、云浮网站制作、云浮网页制作以及云浮网络营销策划等。多年来,我们专注于互联网行业,利用自身积累的技术优势、行业经验、深度合作伙伴关系等,向广大中小型企业、政府机构等提供互联网行业的解决方案,云浮网站推广取得了明显的社会效益与经济效益。目前,我们服务的客户以成都为中心已经辐射到云浮省份的部分城市,未来相信会继续扩大服务区域并继续获得客户的支持与信任!

symbol_priority = {}
symbol_priority[0] = ['#']
symbol_priority[1] = ['(']
symbol_priority[2] = ['+', '-']
symbol_priority[4] = [')']

def comparePriority(symbol, RPN_stack, symbol_stack):
    '''Compare priority between two symbols'''

    global symbol_priority
    if len(symbol_stack) > 0:
        symbol_pop = symbol_stack.pop()
    else:
        return

    for list in symbol_priority.values():
        if (symbol in list) and (symbol_pop in list):
            '''same priority'''
            symbol_stack.append(symbol_pop)
            symbol_stack.append(symbol)
            return
        elif symbol in list:
            '''symbol is smaller'''
            RPN_stack.append(symbol_pop)
            #recusion call
            comparePriority(symbol, RPN_stack, symbol_stack)
            return
        elif symbol_pop in list:
            '''symbol is bigger'''
            symbol_stack.append(symbol_pop)
            symbol_stack.append(symbol)
            return
        else:
            continue

        symbol_stack.append(symbol_pop)
        return

def scanEveryone(input_string, RPN_stack, symbol_stack):
    for ch in input_string:
        if ch.isdigit():
            RPN_stack.append(ch)
        else:
            if len(symbol_stack) > 0:
                if ch == '(':
                    symbol_stack.append(ch)
                elif ch == ')':
                    while True:
                        symbol_pop = symbol_stack.pop()
                        if symbol_pop == '(':
                            break
                        else:
                            RPN_stack.append(symbol_pop)
                else:
                    comparePriority(ch, RPN_stack, symbol_stack)
            else:
                symbol_stack.append(ch)

def scanInput(RPN_stack, symbol_stack):
    input_string = raw_input()
    input_string += '#'
    scanEveryone(input_string, RPN_stack, symbol_stack)

def calRPN(RPN_stack):
    value_stack = []
    RPN_stack.append('#')

    for value in RPN_stack:
        if value == '#':
            return value_stack.pop()
            break
        if value.isdigit():
            value_stack.append(value)
        else:
            right_value = value_stack.pop()
            left_value = value_stack.pop()
            cal_string = left_value + value + right_value
            value_stack.append(str(eval(cal_string)))

def main():
    RPN_stack = []
    symbol_stack = []

    scanInput(RPN_stack, symbol_stack)
    print calRPN(RPN_stack)

if __name__ == '__main__':
    main()

calRPN.py

symbol_priority = {}
symbol_priority[0] = ['#']
symbol_priority[1] = ['(']
symbol_priority[2] = ['+', '-']
symbol_priority[4] = [')']

def comparePriority(symbol, RPN_stack, symbol_stack):
    '''Compare priority between two symbols'''

    global symbol_priority
    if len(symbol_stack) > 0:
        symbol_pop = symbol_stack.pop()
    else:
        return

    for list in symbol_priority.values():
        if (symbol in list) and (symbol_pop in list):
            '''same priority'''
            symbol_stack.append(symbol_pop)
            symbol_stack.append(symbol)
            return
        elif symbol in list:
            '''symbol is smaller'''
            RPN_stack.append(symbol_pop)
            #recusion call
            comparePriority(symbol, RPN_stack, symbol_stack)
            return
        elif symbol_pop in list:
            '''symbol is bigger'''
            symbol_stack.append(symbol_pop)
            symbol_stack.append(symbol)
            return
        else:
            continue

        symbol_stack.append(symbol_pop)
        return

def scanEveryone(input_string, RPN_stack, symbol_stack):
    for ch in input_string:
        if ch.isdigit():
            RPN_stack.append(ch)
        else:
            if len(symbol_stack) > 0:
                if ch == '(':
                    symbol_stack.append(ch)
                elif ch == ')':
                    while True:
                        symbol_pop = symbol_stack.pop()
                        if symbol_pop == '(':
                            break
                        else:
                            RPN_stack.append(symbol_pop)
                else:
                    comparePriority(ch, RPN_stack, symbol_stack)
            else:
                symbol_stack.append(ch)

def scanInput(RPN_stack, symbol_stack):
    input_string = raw_input()
    input_string += '#'
    scanEveryone(input_string, RPN_stack, symbol_stack)

def calRPN(RPN_stack):
    value_stack = []
    RPN_stack.append('#')

    for value in RPN_stack:
        if value == '#':
            return value_stack.pop()
            break
        if value.isdigit():
            value_stack.append(value)
        else:
            right_value = value_stack.pop()
            left_value = value_stack.pop()
            cal_string = left_value + value + right_value
            value_stack.append(str(eval(cal_string)))

def main():
    RPN_stack = []
    symbol_stack = []

    scanInput(RPN_stack, symbol_stack)
    print calRPN(RPN_stack)

if __name__ == '__main__':
    main()

本文名称:python实现逆波兰计算表达式的代码
文章转载:http://myzitong.com/article/ihpjpd.html