On Sat, 15 Feb 2014 12:13:54 +0200, Marko Rauhamaa wrote: > Marko Rauhamaa <ma...@pacujo.net>: > >> 1. if x is y then y ix x >> 2. if x is y and y is z then x is z >> 3. after x = y, x is y >> 4. if x is y, then x == y > > A new attempt: > > 0. x is x > 1. if x is y then y ix x > 2. if x is y and y is z then x is z > 3. after x = y, x is y > 4. if x is y and x == x, then x == y > 5. id(x) == id(y) iff x is y
Python implementations are free to re-use IDs after the object is destroyed. CPython does; Jython and IronPython do not. So #5 needs to point out that the condition id(x) == id(y) only applies if x and y still exist. # Counter-example py> x = 230000 py> idx = id(x) py> del x py> y = 420000 py> idy = id(y) py> idx == idy True (This is *implementation dependent* so your mileage my vary.) > Does that cover it? No. Your definition describes some properties of identity-equivalence, but doesn't explain what identity actually means. -- Steven -- https://mail.python.org/mailman/listinfo/python-list
