On 10/8/06, km <[EMAIL PROTECTED]> wrote: > Hi all, > > > > in the CPython implementation, it's the address where the object is > > stored. but that's an implementation detail. > > ok so can i point a vairiable to an address location just as done in C > language ? > >>> y = 'ATGCATGC' > >>> x = buffer(y) > >>> del(y) > >>> x > <read-only buffer for 0xbf4cf0e0, size -1, offset 0 at 0xbf4cf240> > >>> print x > ATGCATGC > > now even when i delete y, why is that x still exists ?
Say that you copy the contents of file foo into file bar and delete the original foo. Of course file bar still exists in this case. Not much of a difference; I haven't seen buffer objects yet (I am also new to Python), but the initialization for the buffer probably copies whatever is in y somewhere. > thats true even in the case of vairable assignment which states it a a > reference ! > >>> a = 10 > >>> b = a > >>> del(a) > >>> b > 10 > i always thought if u modify the referred variable/buffer object it should > be reflected in the referenced variables/buffers objects You didn't modify the object that the variable /refers to/. Furthermore, numbers are immutable anyway. To continue with the Hindu god analogy, Vishnu did not cease to exist when any of his avatars passed from the physical world; it is no different with objects in Python. IOW a --> 10 b -/ Delete the 'a' reference and: b --> 10 Or: >>> class god(object): ... pass ... >>> vishnu = god() >>> matsya = vishnu >>> kurma = vishnu >>> varaha = vishnu >>> narasimha = vishnu >>> # Etc ... >>> del narasimha >>> matsya <__main__.god object at 0x402e3c6c> >>> kurma <__main__.god object at 0x402e3c6c> What is a little different is this: if there are no references left to an object (such as variables), the object the references point to will eventually be deleted. Variables are one way to have a reference to an object. References to an object may also exist in a list, hash, or other data type. >>> a = 'foo' >>> b = [1,2,3,a] >>> del(a) >>> b [1, 2, 3, 'foo'] > am i wrong ? > does it mean that references in python are not true references ? Python is object-oriented in either sense of the word (think Lisp sense then think Smalltalk sense). These are true references. -- Theerasak -- http://mail.python.org/mailman/listinfo/python-list
