while True:
    try:
        s=input()
#         print(s)
        for each in s:
            if each in ["+","-","*","/"]:
                a,b=map(float,s.split(each))
                
                if each=="+":
                    print("{:.4f}+{:.4f}={:.4f}".format(a,b,a+b))
                elif each=="-":
                    print("{:.4f}-{:.4f}={:.4f}".format(a,b,a-b))
                elif each=="*":
                    print("{:.4f}*{:.4f}={:.4f}".format(a,b,a*b))
                else:
                    if b==0.0:
                        print("Wrong!Division by zero!")
                    else:
                        print("{:.4f}/{:.4f}={:.4f}".format(a,b,a/b))
                break
        else:
            print("Invalid operation!")
                
    except:
        break
    ```
   - split(each) 和判断each in 【】 两个结合,太妙了!