I did the same thing, too, but good job anyway. I would suggest adding another line and importing the math module. (If you do it with the from math import * syntax, then you don't have to put math. in front of every function)

or this: print(eval(input("expression: ")))

Nice I had no idea about that might use it in the future

The problem is it will give an error if you type anything that Python doesn't understand. Use a try except loop for that. Another issue is that it only evaluates one statement then stops. Also, quick warning: https://nedbatchelder.com/blog/201206/eval_really_is_dangerous.html