计算器实现

while True:
    print(li)
    list_ex = re.split('\(([^()]*)\)',li,1)
    print(list_ex)
    if len(list_ex) == 3:
        before = list_ex[0]
        content = list_ex[1]
        after = list_ex[2]
        s1 = eval(content)
        new_ex = before + str(s1) +after
        li = new_ex
    elif len(list_ex) == 1:
        s2 = eval(content)
        print(s2)
        break