I follow head first programming book. When I get to p184, I got stuck. I tried to write the coffee bar POS program as the book suggested. I got something wrong.
When I ran the code, the IDLE showed that File "/Users/.../Documents/Headfirstprogramming/chapter6/pos1.py", line 26, in <module> save_transaction(prices[chioce - 1],credit_card, items[choice - 1])
TypeError: unsupported operand type(s) for -: 'str' and 'int'