[Python-Dev] Issue #26204: compiler now emits a SyntaxWarning on constant statement (original) (raw)
Alexander Walters tritium-list at sdamon.com
Mon Feb 8 15:09:22 EST 2016
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I am not keen on a SyntaxWarning. Either something is python syntax, or it is not. This warning catches something linters have been catching for ages. I really don't see the value in adding this, and can see it causing more confusion than it solves. In the #python irc channel, we see quite a few newbie mistakes, but declaring a constant that isn't used is rarely if ever one of them.
On 2/8/2016 12:44, Victor Stinner wrote:
Hi,
I changed the Python compiler to ignore any kind "constant expressions", whereas it only ignored strings and integers before: http://bugs.python.org/issue26204 The compiler now also emits a SyntaxWarning on such case. IMHO the warning can help to detect bugs for developers who just learnt Python. The warning is not emited for strings, since triple quoted strings are a common syntax for multiline comments. The warning is not emited neither for ellispis (...) since "f(): ..." is a legit syntax for abstract function. Are you ok with the new warning?
New behaviour: haypo at smithers$ ./python Python 3.6.0a0 (default:759a975e1230, Feb 8 2016, 18:21:23)
def f(): ... False ... :2: SyntaxWarning: ignore constant statement
import dis; dis.dis(f) 2 0 LOADCONST 0 (None) 3 RETURNVALUE Old behaviour: haypo at smithers$ python3 Python 3.4.3 (default, Jun 29 2015, 12:16:01) def f(): ... False ... import dis; dis.dis(f) 2 0 LOADCONST 1 (False) 3 POPTOP 4 LOADCONST 0 (None) 7 RETURNVALUE Before strings and numbers were already ignored. Example: haypo at smithers$ python3 Python 3.4.3 (default, Jun 29 2015, 12:16:01) def f(): ... 123 ... import dis; dis.dis(f) 2 0 LOADCONST 0 (None) 3 RETURNVALUE Victor
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