Re: [Jython-users] String Object id question

[D-Man <ds...@ri...>]

On Tue, Mar 27, 2001 at 02:37:15PM -0600, Robert W. Bill wrote:
| 
| I've ran into a bit of confusion with the id() of characters in

strings, not characters.  In (CP|J)ython a character is simply a
string with a length of 1.  In, say,  C | C++ | Java  a char is different
than a   char* , g_string (glib) | char* , std::string (STL) |
java.lang.String

| Jython compared with Python.  Here's something similar to the code
| that started the confusion:
| 
| ----------------------------------------------------------
| S = "abc"
| stringtest = S[1]
| 
| def test(obj1, obj2):
|     if ( id(obj1) != id(obj2) ):
|         return 0
| 
| assert(test(stringtest, S[1])), "String test failed"
| ----------------------------------------------------------
| 
| In CPython, all passes, but in Jython, there's always an AE:
| String test failed.  Is this expected? unavoidable?

I recall hearing that CPython "interns" short strings.  From my
understanding, this basically means that it caches the string object
and uses it for every time that string is used.  There is no guarantee
that any particular string will be interned, it could be an entirely
new object.  It seems that Jython doesn't intern the strings, so they
are new objects.  They should compare as being equal, even though they
are different objects.  

This is just an implementation detail, and CPython optimizes it more
than Jython.

-D