On Sun, Mar 24, 2013 at 12:00 PM, Roy Smith <r...@panix.com> wrote: > I had thought interning only affected > string literals, but apparently it works for all strings! This works > too: > >>>> a = "b" + "ar" >>>> b = "ba" + "r" >>>> id(a) > 3810152 >>>> id(b) > 3810152 > > but, again, none of this is guaranteed.
No, what that proves is that concatenation of literals is treated as a literal. >>> a="foo" >>> b="fo" >>> b+="o" >>> id(a) 14870112 >>> id(b) 15985760 >>> c="fo"+"o" >>> id(c) 14870112 However, you can of course force the matter. >>> a=sys.intern(a) >>> b=sys.intern(b) >>> c=sys.intern(c) >>> id(a),id(b),id(c) (14870112, 14870112, 14870112) (In Python 2, use intern() rather than sys.intern().) It seems that in CPython 3.3.0 on Windows 32-bit (and yes, I do need to be that specific, though this probably applies to a broad range of CPython versions), string literals are interned. But that's an implementation detail. ChrisA -- http://mail.python.org/mailman/listinfo/python-list
