Re: class vs type
On Fri, 19 Oct 2007 12:21:25 -0400, Colin J. Williams wrote: Hrvoje Niksic wrote: Colin J. Williams [EMAIL PROTECTED] writes: In Python Types and Objects, Shalabh Chaturvedi says (in the Python 3.0 documentation - New Style Classes) The term class is traditionally used to imply an object created by the class statement. However, classes are now synonymous with types. Built-in types are usually not referred to as classes. This book prefers using the term type for both built-in and user created types. Do we need two different words to describe what is essentially the same thing? We don't, not anymore, which is why the author chooses the word type for both in the last sentence. In this case, why do we continue to use the word class to generate a type? [snip] Doesn't Python 3 provide an opportunity to move away from discussions about new_style vs old-style? This an opportunity to treat old-style as a historical artefact, not requiring current explanation. So, do we have to decide between 'instance' and 'object' as well? Old-style classes *are* deprecated in favor of new-style classes (whoops!) but the term 'class' is still valid (IMO). It's a common phrase in the OO-world and removing it from a Python programmer's vocabulary (what essentially wouldn't work so well, I suspect) won't help. If you're speaking about just the syntax, well okay, this could be sensible in some unification-focussed vocabulary-minimalistic manner. But combining the class _statement_ and the type _expression_ would essentially change class definitions into expressions. Cheers, Stargaming -- http://mail.python.org/mailman/listinfo/python-list
Re: class vs type
En Fri, 19 Oct 2007 20:14:03 -0300, Colin J. Williams [EMAIL PROTECTED] escribió: The Python 3.0 doc, under Class, has: Programmer’s note: Variables defined in [...] For new-style classes, descriptors can be used to create instance variables with different implementation details. Presumably, it is intended that every class implicitly inherits from object? For Python 3.0, yes. Where did you read the above text? The 3.0 docs at http://docs.python.org/dev/3.0/reference/compound_stmts.html#class-definitions are already updated and don't menction new-style classes at all. -- Gabriel Genellina -- http://mail.python.org/mailman/listinfo/python-list
Re: class vs type
Terry Reedy wrote: Colin J. Williams [EMAIL PROTECTED] wrote in message news:[EMAIL PROTECTED] | Doesn't Python 3 provide an opportunity | to move away from discussions about | new_style vs old-style? This an | opportunity to treat old-style as a | historical artefact, not requiring | current explanation. Yes, there will not be 'old-style' classes in Py3 and 3.0 doc will not mention them.. But we are actually at 2.5 and there will be 2.6, 2.7, 2.8? that still have them. Terry, Thanks for clarifying the intent. The Python 3.0 doc, under Class, has: Programmer’s note: Variables defined in the class definition are class variables; they are shared by all instances. To define instance variables, they must be given a value in the __init__() method or in another method. Both class and instance variables are accessible through the notation “self.name“, and an instance variable hides a class variable with the same name when accessed in this way. Class variables with immutable values can be used as defaults for instance variables. For new-style classes, descriptors can be used to create instance variables with different implementation details. Presumably, it is intended that every class implicitly inherits from object? Colin W. -- http://mail.python.org/mailman/listinfo/python-list
Re: class vs type
On Fri, 19 Oct 2007 12:21:25 -0400, Colin J. Williams wrote:
In this case, why do we continue to use the word class to generate a
type?
Because type is a callable, and class is convenient syntactic sugar.
class Parrot(object):
def speak(self, msg):
return Polly sez %s % msg
is much more convenient than:
import new
Parrot = type('Parrot', (object,),
{'speak': lambda self, msg: 'Polly sez %s' % msg})
particularly for large classes with many methods.
--
Steven
--
http://mail.python.org/mailman/listinfo/python-list
Re: class vs type
Colin J. Williams [EMAIL PROTECTED] wrote in message news:[EMAIL PROTECTED] | Doesn't Python 3 provide an opportunity | to move away from discussions about | new_style vs old-style? This an | opportunity to treat old-style as a | historical artefact, not requiring | current explanation. Yes, there will not be 'old-style' classes in Py3 and 3.0 doc will not mention them.. But we are actually at 2.5 and there will be 2.6, 2.7, 2.8? that still have them. -- http://mail.python.org/mailman/listinfo/python-list
Re: class vs type
Hrvoje Niksic wrote: Colin J. Williams [EMAIL PROTECTED] writes: In Python Types and Objects, Shalabh Chaturvedi says (in the Python 3.0 documentation - New Style Classes) The term class is traditionally used to imply an object created by the class statement. However, classes are now synonymous with types. Built-in types are usually not referred to as classes. This book prefers using the term type for both built-in and user created types. Do we need two different words to describe what is essentially the same thing? We don't, not anymore, which is why the author chooses the word type for both in the last sentence. In this case, why do we continue to use the word class to generate a type? But, as the author correctly explains, class and type used to not be the same thing. Classes were created with 'class', and they were fundamentally different from C types created in extension modules. All instances of old-style classes are of type 'instance', which is why they have the __class__ attribute, so you can find their actual class. (Functions like isinstance contain hacks to support old-style classes.) New-style classes elevate Python-level classes to types equal to the built-in ones, which is why the word type is now sufficient for both. Doesn't Python 3 provide an opportunity to move away from discussions about new_style vs old-style? This an opportunity to treat old-style as a historical artefact, not requiring current explanation. Colin W. -- http://mail.python.org/mailman/listinfo/python-list
Re: class vs type
Colin J. Williams [EMAIL PROTECTED] writes: In Python Types and Objects, Shalabh Chaturvedi says (in the Python 3.0 documentation - New Style Classes) The term class is traditionally used to imply an object created by the class statement. However, classes are now synonymous with types. Built-in types are usually not referred to as classes. This book prefers using the term type for both built-in and user created types. Do we need two different words to describe what is essentially the same thing? We don't, not anymore, which is why the author chooses the word type for both in the last sentence. But, as the author correctly explains, class and type used to not be the same thing. Classes were created with 'class', and they were fundamentally different from C types created in extension modules. All instances of old-style classes are of type 'instance', which is why they have the __class__ attribute, so you can find their actual class. (Functions like isinstance contain hacks to support old-style classes.) New-style classes elevate Python-level classes to types equal to the built-in ones, which is why the word type is now sufficient for both. -- http://mail.python.org/mailman/listinfo/python-list
class vs type
In Python Types and Objects, Shalabh Chaturvedi says (in the Python 3.0 documentation - New Style Classes) The term class is traditionally used to imply an object created by the class statement. However, classes are now synonymous with types. Built-in types are usually not referred to as classes. This book prefers using the term type for both built-in and user created types. Do we need two different words to describe what is essentially the same thing? Colin W. -- http://mail.python.org/mailman/listinfo/python-list
