I once had the surprising experience of having to help a postdoc with a PhD in mechanical engineering wrap his head around a block of Python code he was reading

I once had the surprising experience of having to help a postdoc with a PhD in mechanical engineering wrap his head around a block of Python code he was reading that looked like: x = f0() x = f1(x) He was just mentally blocked on how all of these things could be true at the same time, and/or on how a variable could be used in setting its own value, since assigning a new value to x would change the value that had been passed to f1! His intuition was that this meant some kind of recursion-to-stability was at play. All he needed was to be informed that this could be equivalently represented as x = f0() y = f1(x) or x = f1(f0())