#__author__:"Jay guo" #__date__:2016/9/12 import re def check(s):     if re.findall("[a-zA-Z]",s):         return "quit"     else:         return s def format(s):     s = s.replace(" ","")     s = s.replace("++","+")     s = s.replace("+-","-")     s = s.replace("-+","-")     s = s.replace("--","+")     return s def mul_exc(s):     while True:         ret = re.search("\d+\.?\d*[*/][+-]?\d+\.?\d*", s)         if ret:             x,y = re.split("[*/]",ret.group())             x = float(x)             y = float(y)             if "*" in ret.group():                 end = x*y             else:                 end = x/y             s = s.replace(ret.group(),str(end))         else:             break     return s def add_sub(s):     while True:         ret = re.search("\d+\.?\d*[+-]\d+\.?\d*", s)         if ret:             x,y = re.split("[+-]", ret.group())             x = float(x)             y = float(y)             if "+" in ret.group():                 end = x + y             else:                 end = x - y             s = s.replace(ret.group(), str(end))         else:             break     s = s.replace("(","")     s = s.replace(")","")     return s def main():     while True:         user = input("PLZ input>>>>:  ")         user = check(user)         if user == "quit":             print ("False")             continue         user = format(user)         user = "(" + user + ")"         while True:             ret = re.search("\([^()]*\)",user)             if ret:                 ret = ret.group()                 ret1 = mul_exc(ret)                 ret1 = add_sub(ret1)                 user = user.replace(ret,ret1)                 user = format(user)             else:                 user = add_sub(user)                 break         print("结果",user) main()