On Thu, Apr 26, 2018 at 6:30 PM, Antoine Pitrou email@example.com wrote:
On Thu, 26 Apr 2018 17:29:17 +1000 Steven D'Aprano firstname.lastname@example.org wrote:
On Thu, Apr 26, 2018 at 07:16:28PM +1200, Greg Ewing wrote:
Tim Peters wrote:
As a statement in a program (as opposed to typed at a shell), "a := 3" has the unnecessary (in that context) property of returning (and discarding 3), so it's better style to use "a = 3" in that context.
That seems like a post-hoc justification. If := were the one and only assignment symbol, the compiler could easily optimise away the extra DUP_TOP or whatever is involved.
Its still bad form to rely on compiler-dependent optimizations which aren't part of the language specification.
If such were the need, you could very well make it part of the language
specification. We are talking about a trivial optimization that any
runtime could easily implement (e.g. if a sequence
POP_TOP occurs, replace it with
Not at the REPL, no. At the REPL, you need to actually print out that value. It's semantically different.
Any runtime already has to implement a set of performance properties that's far less trivial than that. For example, any decent runtime is expected to provide amortized O(1) list append or dict insertion. You are breaking user expectations if you don't.
You assume that, but it isn't always the case. Did you know, for instance, that string subscripting (an O(1) operation in CPython) is allowed to be O(n) in other Python implementations?
Now you do.