[Tim]
Which this alternative expresses directly:
if (diff := x - x_base) and (g := gcd(diff, n)) > 1: return g
That's so Pythonic I could cry ;-)
[Antoine]
It looks like C to me. That won't make me cry (I write C++ code daily these days), but it's certainly not the same language as Python.
The second part, especially, where you use the result of an assignment expression as a comparison operand, looks definitely un-Pythonic.
You snipped the part explaining _what's_ "Pythonic" about it: It's _really_ an "and" test: if the diff isn't 0 and gcd(diff, n) > 1, return the gcd. That's how I _thought_ of it from the start. "Expresses directly" is the Pythonic part; the syntax is minor to me. Seeing that the _intent_ is an "and test" is a pattern-matching puzzle in the original spelling (which essentially turned me into a compiler, writing low-level code for the _concepts_ I had in mind from the start): diff = x - x_base if diff: g = gcd(diff, n) if g > 1: return g But note that the part of the PEP I support is just the "binding expression" part: giving a simple name (binding an identifier) to the result of an expression. I don't want the full potential complexity of assignment statements in expressions. There's nothing "un-Pythonic" about merely giving a name to an expression result, apart from that there are few contexts that currently support that in a sanely usable way.