python实现逆波兰计算表达式的代码-创新互联

如下资料是关于python实现逆波兰计算表达式的代码。

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()

另外有需要云服务器可以了解下创新互联cdcxhl.cn，海内外云服务器15元起步，三天无理由+7*72小时售后在线，公司持有idc许可证，提供“云服务器、裸金属服务器、高防服务器、香港服务器、美国服务器、虚拟主机、免备案服务器”等云主机租用服务以及企业上云的综合解决方案，具有“安全稳定、简单易用、服务可用性高、性价比高”等特点与优势，专为企业上云打造定制，能够满足用户丰富、多元化的应用场景需求。