Glenn Linderman wrote:
If Py_None corresponds to None in Python syntax ... then it is a fixed constant and could be left global, probably.
No, it couldn't, because it's a reference-counted object like any other Python object, and therefore needs to be protected against simultaneous refcount manipulation by different threads. So each interpreter would need its own instance of Py_None. The same goes for all the other built-in constants and type objects -- there are dozens of these.
The cost is one more push on every function call,
Which sounds like it could be a rather high cost! If (just a wild guess) each function has an average of 2 parameters, then this is increasing the amount of argument pushing going on by 50%...
On many platforms, there is the concept of TLS, or thread-local storage.
That's another possibility, although doing it that way would require you to have a separate thread for each interpreter, which you mightn't always want. -- Greg -- http://mail.python.org/mailman/listinfo/python-list
