Molecular mass calculator. Not Perfect

something.py

#!/usr/bin/env python

import getpass # This module is imported only for the purpose of printing out your user
import re
from molmass import *

name = getpass.getuser()

print(f"Hello,{name}") # Prints current username
input = str(input("Please enter in chemical formula: ")) #assign string the chemical formula

if input == "": #If statement to see if user has left input blank
    print("You forgot to type in formula")
else:
    f = Formula(input) #converts input to "formula"
    mf = f.mass #variable assigned to mass of "f"
    print(f"your formula is {input}") #prints what user has assigned variable input
    print(f"Your total mass is {mf}.") #prints mass of formula
    print(f"Below is the composition fo {input}")
    print(f.composition())

#TODO: Put some sort of way to restart the program without reopening it