Re: [Python-Dev] 'fast locals' in Python 2.5
Hi, On Wed, Jun 07, 2006 at 02:07:48AM +0200, Thomas Wouters wrote: > I just submitted http://python.org/sf/1501934 and assigned it to Neal so it > doesn't get forgotten before 2.5 goes out ;) It seems Python 2.5 compiles > the following code incorrectly: No, no, it's an underground move by Jeremy to allow assignment to variables of enclosing scopes: [in 2.5] def f(): x = 5 def g(): x += 1 g() print x # 6 The next move is to say that this is an expected feature of the augmented assignment operators, from which it follows naturally that we need a pseudo-augmented assignment that doesn't actually read the old value: [in 2.6] def f(): x = 5 def g(): x := 6 g() print x# 6 Credits to Samuele's evil side for the ideas. His non-evil side doesn't agree, and neither does mine, of course :-) More seriously, a function with a variable that is only written to as the target of augmented assignments cannot possibly be something else than a newcomer's mistake: the augmented assignments will always raise UnboundLocalError. Maybe this should be a SyntaxWarning? A bientot, Armin ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
[Python-Dev] 'fast locals' in Python 2.5
I just submitted http://python.org/sf/1501934 and assigned it to Neal so it doesn't get forgotten before 2.5 goes out ;) It seems Python 2.5 compiles the following code incorrectly: >>> g = 1>>> def f1():... g += 1... >>> f1()>>> g2It looks like the compiler is not seeing augmented assignment as creating a local name, as this fails properly: >>> def f2():... g += 1... g = 5... >>> f2()Traceback (most recent call last): File "", line 1, in File "", line 2, in f2 UnboundLocalError: local variable 'g' referenced before assignmentThe dis.dis output confirms this:>>> dis.dis(f1) 1 0 LOAD_GLOBAL 0 (g) 3 LOAD_CONST 1 (1) 6 INPLACE_ADD 7 STORE_GLOBAL 0 (g) 10 LOAD_CONST 0 (None) 13 RETURN_VALUE If anyone feels like fixing it and happens to remember where the new compiler does the fast-locals optimization (I recall a few people were working on extra optimizations and all), please do :-) (I can probably look at it before 2.5 if no one else does, though.) It may be a good idea to check for more such cornercases while we're at it (but I couldn't find any in the fast-locals bit.)-- Thomas Wouters < [EMAIL PROTECTED]>Hi! I'm a .signature virus! copy me into your .signature file to help me spread! ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
