The f-string f"{x=}" expands to f"x={x}"

It supports both single variables and more complex expressions. Here’s a few examples:

>>> x = 42
>>> f"{x=}"
'x=42'
>>> f"{1+2=}"
'1+2=3'
>>> f"{(1+2)*3=}"
'(1+2)*3=9'

This is described in What’s New In Python 3.8;

(via)