Other languages do this sort of thing, so certainly it "would work". But it's very much counter to the design and aesthetics of Python.
Python is intended to enforce a strong distinction between statements and expressions (`:=` notwithstanding :/) because it sidesteps a lot of questions that one might otherwise ask about how it's intended to be parsed (including by humans).
Being able to write something like your example makes it harder to figure out where the end is, figure out what happens if there's more than one statement inside an `if` (do we only consider the result of the last expression? What if the last thing isn't an expression?), etc. By the time you get to the end of understanding what's happening inside the block, you can lose the context that the result is being assigned to `x`.
At the other extreme, everything is an expression, and you have Lisp with funky syntax. But Python holds that this syntactic structure is important for understanding the code. I sense that this is part of what "Flat is better than nested" is intended to mean.
Python is intended to enforce a strong distinction between statements and expressions (`:=` notwithstanding :/) because it sidesteps a lot of questions that one might otherwise ask about how it's intended to be parsed (including by humans).
Being able to write something like your example makes it harder to figure out where the end is, figure out what happens if there's more than one statement inside an `if` (do we only consider the result of the last expression? What if the last thing isn't an expression?), etc. By the time you get to the end of understanding what's happening inside the block, you can lose the context that the result is being assigned to `x`.
At the other extreme, everything is an expression, and you have Lisp with funky syntax. But Python holds that this syntactic structure is important for understanding the code. I sense that this is part of what "Flat is better than nested" is intended to mean.