使用Python实现一种算数表达式求值的算法，模拟这种使用栈的方式，这是由E.W.Dijkstra在20世纪60年代发明的一种非常简单的算法。代码模拟仅仅表现一种编程思想，代码的逻辑并不完全：
if __name__ == "__main__": cal_str = input("请输入算数表达式（e.g.(((1+2)*(3+5))+2), 只适合简单的算数表达式）：") num_stack = [] symbol_stack = [] for chr in cal_str: #print(chr) if chr == "(": continue elif chr == "" or chr == "\t" or chr == "\n": continue elif chr == "+": symbol_stack.append(chr) elif chr == "-": symbol_stack.append(chr) elif chr == "*": symbol_stack.append(chr) elif chr == "/": symbol_stack.append(chr) elif chr == "sqrt": symbol_stack.append(chr) elif chr == ")": total_num = num_stack.pop() now_symbol = symbol_stack.pop() if now_symbol == "+": total_num += num_stack.pop() if now_symbol == "-": total_num -= num_stack.pop() if now_symbol == "*": total_num *= num_stack.pop() if now_symbol == "/": total_num /= num_stack.pop() num_stack.append(total_num) else: num_stack.append(int(chr)) print(num_stack.pop())
原文：https://www.cnblogs.com/frisk/p/11625347.html