When not to use f-strings?

[perfringo]

just to mention that if there is need for escaping within placeholder than it's a case of having expression IN the placeholder. In this case it would be better and more readable to have the expression prepared and assigned to a variable beforehand and use that variable in the f-string

To showcase buran's suggestion:

>>> newline = '\n'                                                        
>>> first = 'first'                                                       
>>> second = 'second'  
>>> print(f'{first}{newline}{second}')
first
second