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@smithers$ ./python
Python 3.6.0a0 (default:759a975e1230, Feb 8 2016, 18:21:23)
def f():
... False
...
<stdin>:2: SyntaxWarning: ignore constant statement
import dis; dis.dis(f)
2 0 LOAD_CONST 0 (None)
3 RETURN_VALUE
Old behaviour:
haypo@smithers$ python3
Python 3.4.3 (default, Jun 29 2015, 12:16:01)
def f():
... False
...
import dis; dis.dis(f)
2 0 LOAD_CONST 1 (False)
3 POP_TOP
4 LOAD_CONST 0 (None)
7 RETURN_VALUE
Before strings and numbers were already ignored. Example:
haypo@smithers$ python3
Python 3.4.3 (default, Jun 29 2015, 12:16:01)
def f():
... 123
...
import dis; dis.dis(f)
2 0 LOAD_CONST 0 (None)
3 RETURN_VALUE
Victor
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