The definition of an object in Python

[Michele Simionato]

Andrew Koenig <ark at acm.org> wrote in message news:<yu991xwuiac7.fsf at tinker.research.att.com>...
> Avi>   Wesley says that every Python object must possess the following
> Avi>   three characteristics: 1) an identity, which can be retrieved 
> Avi>   by the function id(); 2) a type, which can be retrieved by
> Avi>   the function type(); and 3) a value.
> 
> Avi>   But when I do the following
> 
> Avi>       mystring = 'hello'
> 
> Avi>       print mystring.id()
> 
> Avi>       print mystring.type()
> 
> Avi>   Python complains that mystring does not possess the attributes
> Avi>   id and type.
> 
> type and id are functions, not methods.
> 
> >>> mystring = 'hello'
> >>> print mystring.id()         # using id as a method doesn't work
> Traceback (most recent call last):
>   File "<stdin>", line 1, in ?
> AttributeError: 'str' object has no attribute 'id'
> >>> print id(mystring)          # using id as a function does
>  1456272
> >>> print type(mystring)        # ditto for type
> <type 'str'>

Just for fun, to show that the built-ins "id" and "type" are  regular objects:

>>> id(id)
1076547724
>>> type(type)
<type 'type'>
>>> type(id)
<type 'builtin_function_or_method'>
>>> id(type)
135272896


Michele