On 10/8/06, km <[EMAIL PROTECTED]> wrote:
>
> Hi all,
>
> was looking at references in python...
> >>> a = 10
> >>> b = a
> >>> id(a)
> 153918788
> >>>id(b)
> 153918788
>
> where a and b point to the same id. now is this id an address ?
The id may be considered similar to an address in C, etc. slightly
different but conceptually close.
> can one dereference a value based on address alone in python?
Not to my knowledge. Generally speaking, you wouldn't want to anyway.
> is id similar to the address of a variable or a class ?
Exactly. Similar. Not the same, but similar.
> read abt buffers as a refernce to a buffer object.
> actually i tried passing list and dict types to buffer function, but only
> with string type i could createa buffer reference,
> >>>y = 'GATCGTACC'
> >>>x = buffer(y, 0,8)
> >>> x
> <read-only buffer for 0xbf4cd3b8, size 8, offset 2 at 0xbf4cf0e0>
> >>>print x
> TCGTACC
> >>> id(y)
> -1085484104
> >>> id(x)
> -1085476384
>
> now the ids of y and x are not the same - why ?
You assigned two different object values to these names. In Python, a
name is just a name. It can point at any object. This relation becomes
very clear with mutable objects.
>>> x = {'foo':42, 'bar':69}
>>> id(x)
1076761980
>>> y = x
>>> y['baz'] = 36
>>> id(y)
1076761980
>>> y
{'baz': 36, 'foo': 42, 'bar': 69}
>>> x
{'baz': 36, 'foo': 42, 'bar': 69}
When I wrote y = x, all I did was make the variable y point to the
dictionary object x is also pointing at. Hence they point to the same
object. Things would be different if I decided to copy an object
instead:
>>> x = {'foo':42, 'bar':69}
>>> import copy
>>> y = copy.deepcopy(x)
>>> y['baz'] = 36
>>> id(x)
1076761164
>>> id(y)
1076890180
>>> x
{'foo': 42, 'bar': 69}
>>> y
{'baz': 36, 'foo': 42, 'bar': 69}
Since your name is Sri Krishna, an avatar of Vishnu, the concept
should be familiar. Variables are like avatars; they represent the
object (whether this is a humble dictionary or Vishnu the Preserver)
for the user, and serve as a bridge between the computer and the user,
as an avatar of Vishnu is a bridge between the physical world and the
supernatural.
Dasha Avatar -- one god. Think about it.
> what exactly are buffer object types ? and how can i instantiate them ?
If you want to get a line of user input, the basic function is raw_input().
-- Theerasak
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