On 17 mayo, 00:52, Patrick Maupin <pmau...@gmail.com> wrote: > On May 16, 5:38 pm, James Mills <prolo...@shortcircuit.net.au> wrote: > > > On Mon, May 17, 2010 at 8:26 AM, vsoler <vicente.so...@gmail.com> wrote: > > > However, can I be 100% sure that,no matter how I access variable > > > 'x' (with config.x or mod.config.x) it is always the same 'x'. I mean > > > that either reference of 'x' points to the same id(memory position)? > > > Yes it does unless you re-assign it. > > > --James > > To expand a bit on what James is saying: > > If, for example, inside your main module, you got tired of typing > "mod.config.x" everywhere you were using it, and decided that you > could make a local reference to the same variable: > > x = mod.config.x > > Now, whenever you use just plain x inside the main module, you are > also referencing the exact same object, *until* some other function > decides to do: > > mod.config.x = y > > At this point in time, the 'x' inside main references the object that > mod.config.x originally referenced, but mod.config.x now references a > different object. > > Unlike C, for example, where the assignment operator physically places > an item into a specific memory location (either fixed globally or > within a stack frame), the assignment operator in python simply stores > a key/value pair into a namespace dictionary. So whenever you > retrieve a value from the dictionary using that key, you will get the > value that was last associated with that key. > > So, 'mod.config.x' will first retrieve the object associated with the > key 'mod' from the main module's namespace dictionary, then will > retrieve the object associated with the key 'config' from that > module's namespace dictionary, then will retrieve the object > associated with the key 'x' from that module's namespace dictionary. > Unless you later modify any of those key/value pairs, subsequent > retrieval will always result in the same final value. > > Regards, > Pat
Really interesting, it helps a lot. Thank you -- http://mail.python.org/mailman/listinfo/python-list
