Em Sáb, 2006-03-25 às 09:11 -0800, Ziga Seilnacht escreveu: > Python has a special internal list of integers in which it caches > numbers smaller than 1000 (I'm not sure that the number is correct), > but that is an implementation detail and you should not rely on it.
By testing: >>> a = 10 >>> b = 10 >>> a is b True >>> a = 100 >>> b = 100 >>> a is b False >>> a = 50 >>> b = 50 >>> a is b True >>> a = 70 >>> b = 70 >>> a is b True >>> a = 99 >>> b = 99 >>> a is b True And to the other side: >>> a = -10 >>> b = -10 >>> a is b False >>> a = -5 >>> b = -5 >>> a is b True >>> a = -6 >>> b = -6 >>> a is b False And then, when looking to Python 2.4's code[1]: """ #ifndef NSMALLPOSINTS #define NSMALLPOSINTS 100 #endif #ifndef NSMALLNEGINTS #define NSMALLNEGINTS 5 #endif #if NSMALLNEGINTS + NSMALLPOSINTS > 0 /* References to small integers are saved in this array so that they can be shared. The integers that are saved are those in the range -NSMALLNEGINTS (inclusive) to NSMALLPOSINTS (not inclusive). */ static PyIntObject *small_ints[NSMALLNEGINTS + NSMALLPOSINTS]; #endif """ However, as stated before, don't rely on these numbers. The trunk[2] defines now 256, not 99, as the biggest integer shared. [1] http://svn.python.org/projects/python/tags/release24-fork/Objects/intobject.c [2] http://svn.python.org/projects/python/trunk/Objects/intobject.c HTH, -- Felipe. -- http://mail.python.org/mailman/listinfo/python-list
