This is the code. The second line doesn't make much sense to me. Can anyone please help?
for key, value in roman_map.items():
s = s.replace(key, f'+{value}')
return eval(s)
It's just for formatting the string, for example if the variable value is 3, then f'+{value}' would result as a formatted string '+3'. If this doesn't satisfy you, then I think I know what's confusing you, the line s = s.replace(key, f'+{value}') is a simple line which is for replacing a part of a string. As I see it, s is a pre defined variable with a string(it's written s = s.replace in the line, the replace method belongs to a string so most likely s is a string variable) so what this line does is, in the for loop, you see the key variable, now the replace method takes two parameters, the first one asks the user which part of the string to replace and the second specifies what to replace it with, henceforth I can say this much that this line replaces the part of the string which is same as whatever value the variable key holds during the current iteration(in simple english, the current loop number) with f'+{value}'.(Read my answer from the starting in case you forgot what that line means or if your confused, if this still doesen't satisfy you, try googling the string replace method and f strings in python)