How can this line raise an 'ValueError: Invalid format specifier' in python?

Question

I wrote this line of code, to format a message, but it gives me this error:

Traceback (most recent call last):
  File "yes.py", line 221, in buy_stock
    message = f'{"action": "Bought {amount} stocks", "current-money": "{self.money}", "money-combined": "{self.money_combined}", "stocks" : "{self.stock_amount}"}'
ValueError: Invalid format specifier

Written in python3.8, all variables are defined. Im trying to make this message in json format, so i can send it to a server, which does some info harvesting on the data.

Answer 1

Enclose with one more pair of curly braces, as shown below

message = f'{{"action": "Bought {amount} stocks", "current-money": "{self.money}", "money-combined": "{self.money_combined}", "stocks" : "{self.stock_amount}"}}'