class declaration shortcut

[=?iso-8859-1?q?Luis_M._Gonz=E1lez?=]

I've come across a code snippet in www.rubyclr.com where they show how
easy it is to declare a class compared to equivalent code in c#.
I wonder if there is any way to emulate this in Python.

The code is as follows:

Person = struct.new( :name, :birthday, :children)

I tried something like this, but it's nothing close to what I'd like:

def klass(table, *args):
cls = new.classobj(ta ble, (), {})
for i in args:
setattr(cls, i, i)
return cls

But this above is not what I want.
I guess I should find a way to include the constructor code inside
this function, but I don't know if this is possible.
Also, I wonder if there is a way to use the variable name in order to
create a class with the same name (as in "Person"abo ve).

Well, if anyone has an idea, I'd like to know...

Luis

[Bruno Desthuilliers]

Luis M. González a écrit :

I've come across a code snippet in www.rubyclr.com where they show how
easy it is to declare a class compared to equivalent code in c#.
I wonder if there is any way to emulate this in Python.

The code is as follows:

Person = struct.new( :name, :birthday, :children)

s/struct/Struct/

I tried something like this, but it's nothing close to what I'd like:

def klass(table, *args):
cls = new.classobj(ta ble, (), {})
for i in args:
setattr(cls, i, i)
return cls

But this above is not what I want.
I guess I should find a way to include the constructor code inside
this function, but I don't know if this is possible.
Also, I wonder if there is a way to use the variable name in order to
create a class with the same name (as in "Person"abo ve).

Well, if anyone has an idea, I'd like to know...

Here's a *very* Q&D attempt - that doesn't solve the name problem:
def Struct(name, *attribs):
args = ", ".join("%s=None " % attr for attr in attribs)
body = "\n ".join("sel f.%s = %s" % (attr, attr) \
for attr in attribs)
source = ("""
class %s(object):
def __init__(self, %s):
%s
""".strip() ) % (name, args, body)
#print source
code = compile(source, 'dummy', 'single')
exec code
return locals()[name]

But note that I'd immediatly fire anyone using such an abomination in
production code.

[Steven Bethard]

Luis M. González wrote:

I've come across a code snippet in www.rubyclr.com where they show how
easy it is to declare a class compared to equivalent code in c#.
I wonder if there is any way to emulate this in Python.

The code is as follows:

Person = struct.new( :name, :birthday, :children)

How about something like::

class Person(Record):
__slots__ = 'name', 'birthday', 'children'

You can then use the class like::

person = Person('Steve', 'April 25', [])
assert person.name == 'Steve'
assert person.birthday == 'April 25'
assert not person.children

Is that what you were looking for? If so, the recipe for the Record
class is here:

http://aspn.activestate.com/ASPN/Coo.../Recipe/502237

STeVe

[=?iso-8859-1?q?Luis_M._Gonz=E1lez?=]

On Feb 28, 6:21 pm, Steven Bethard <steven.beth... @gmail.comwrote :

Luis M. González wrote:

I've come across a code snippet inwww.rubyclr.c omwhere they show how
easy it is to declare a class compared to equivalent code in c#.
I wonder if there is any way to emulate this in Python.

The code is as follows:

Person = struct.new( :name, :birthday, :children)

How about something like::

class Person(Record):
__slots__ = 'name', 'birthday', 'children'

You can then use the class like::

person = Person('Steve', 'April 25', [])
assert person.name == 'Steve'
assert person.birthday == 'April 25'
assert not person.children

Is that what you were looking for? If so, the recipe for the Record
class is here:

http://aspn.activestate.com/ASPN/Coo.../Recipe/502237

STeVe

Hmmm... not really.
The code above is supposed to be a shorter way of writing this:

class Person:
def __init__(self, name, birthday, children):
self.name = name
self.birthday = birthday
self.children = children

So the purpose of this question is finding a way to emulate this with
a single line and minimal typing.

There are a few problems here:
1) How to get the variable name (in this case "Person") become the
name of the class without explicity indicating it.
2) How to enter attribute names not enclosed between quotes. The only
way I can do it is by entering them as string literals.

It's not that I desperately need it, but I'm just curious about it...

Luis

[Steven Bethard]

Luis M. González wrote:

On Feb 28, 6:21 pm, Steven Bethard <steven.beth... @gmail.comwrote :

>How about something like::

class Person(Record):
__slots__ = 'name', 'birthday', 'children'

You can then use the class like::

person = Person('Steve', 'April 25', [])
assert person.name == 'Steve'
assert person.birthday == 'April 25'
assert not person.children

Is that what you were looking for? If so, the recipe for the Record
class is here:

http://aspn.activestate.com/ASPN/Coo.../Recipe/502237

[snip]

Hmmm... not really.
The code above is supposed to be a shorter way of writing this:

class Person:
def __init__(self, name, birthday, children):
self.name = name
self.birthday = birthday
self.children = children

So the purpose of this question is finding a way to emulate this with
a single line and minimal typing.

That __init__ is exactly what was generated in my example above. So
you're mainly objecting to using two-lines? You can make it a one-liner
by writing::

class Person(Record): __slots__ = 'name', 'birthday', 'children'

1) How to get the variable name (in this case "Person") become the
name of the class without explicity indicating it.

The only things that know about their own names are class statements
(through metaclasses) so you can't really do it without a class
statement of some sort (which means you'll have to use two lines).

2) How to enter attribute names not enclosed between quotes. The only
way I can do it is by entering them as string literals.

If you're really bothered by quotes, a pretty minimal modification to
the recipe could generate the same code from:

class Person(Record): slots = 'name birthday children'

STeVe

[Bjoern Schliessmann]

Luis M. González wrote:

I've come across a code snippet in www.rubyclr.com where they show
how easy it is to declare a class compared to equivalent code in
c#. I wonder if there is any way to emulate this in Python.

The code is as follows:

Person = struct.new( :name, :birthday, :children)

What's easy about this?

Also, this is a definition and not just a declaration.

But this above is not what I want.
I guess I should find a way to include the constructor code inside
this function, but I don't know if this is possible.

Could you please describe what exactly you want in an abstract way?

Also, I wonder if there is a way to use the variable name in order
to create a class with the same name (as in "Person"abo ve).

Two classes with the same name?

In Python, classes have no name. They are anonymous objects which
can be bound to names.

Regards,
Björn

--
BOFH excuse #367:

Webmasters kidnapped by evil cult.

[Bruno Desthuilliers]

Bjoern Schliessmann a écrit :
(snip)

In Python, classes have no name.

class Toto(object):
pass

print Toto.__name__

[Bjoern Schliessmann]

Bruno Desthuilliers wrote:

class Toto(object):
pass

print Toto.__name__

Okay, I revoke my statement and assert the opposite.

But what's it (__name__) good for?

Regards,
Björn

--
BOFH excuse #179:

multicasts on broken packets

[Marc 'BlackJack' Rintsch]

In <54************ *@mid.individua l.net>, Bjoern Schliessmann wrote:

Bruno Desthuilliers wrote:

>class Toto(object):
pass

print Toto.__name__

Okay, I revoke my statement and assert the opposite.

But what's it (__name__) good for?

As objects don't know to which name they are bound, that's a good way to
give some information in stack traces or when doing introspection.

Ciao,
Marc 'BlackJack' Rintsch

[Michele Simionato]

On Mar 1, 9:40 am, Marc 'BlackJack' Rintsch <[e-mail] wrote:

In <54msaoF21c6h.. [e-mail] l.net>, Bjoern Schliessmann wrote:

But what's it (__name__) good for?

As objects don't know to which name they are bound, that's a good way to
give some information in stack traces or when doing introspection.

Also, the name is used by pickle to find the class of pickled
instances.

Michele Simionato