Ramashish Baranwal <[EMAIL PROTECTED]> wrote:
> > > I want a way to get the contents in the order of their declaration,
> > > i.e. [B, A, D]. Does anyone know a way to get it?
> >
> > My suggestion would be to actually parse the text of the module. "Brute
> > force" is what it's called ;). But doing so with, say, pyparsing
> > shouldn't be *very* difficult.
> >
> > Just out of curiosity: Why do you need the order?
> >
> Thank you for your replies, and sorry for my late response.
>
> Gabriel, unfortunately I am not a python expert so don't know how to
> play with module creation. I tried to look into __import__ function,
> but can't see a way to get what I want.
>
> Wildemar, your approach seems workable. I am going to have a look at
> it.
>
> Well, my requirement doesn't turn out to be an actual requirement
> now.:) I am using a web framework Django, that lets you define classes
> for database tables. The classes so defined can refer to other classes
> representing db tables. It also allows you to export those table data
> in a db-neutral format e.g. xml via the python classes so defined.
> Exporting does not require an order, but I thought that importing the
> data back may require data of classes which are referred by other
> classes to be present. I just verified that its not so. So I don't
> need to do it immediately.
Actually I had a requirement to do exactly this. I was using python
as a definition language, making classes to define other things. It
worked very nicely but I needed to get the classes in definition
order.
Here is how I did it with metaclasses
class _Definition_Metaclass(type):
"""
A metaclass to add a _class_sequence attribute to each definition so we know
which order they were defined in.
"""
_class_sequence = 0
def __init__(cls, name, bases, dict):
_class_sequence = _Definition_Metaclass._class_sequence
_Definition_Metaclass._class_sequence += 1
cls._class_sequence = _class_sequence
class Definition(object):
__metaclass__ = _Definition_Metaclass
class A(Definition): pass
class B(A): pass
class C(A): pass
class D(Definition): pass
class E(C): pass
objects = []
for obj in locals().values():
try:
if issubclass(obj, Definition):
objects.append(obj)
except TypeError:
pass
objects_sorted = sorted(objects, key=lambda x: x._class_sequence)
print objects
# Gives something like
# [<class '__main__.A'>, <class '__main__.Definition'>, <class
# '__main__.C'>, <class '__main__.B'>, <class '__main__.E'>, <class
# '__main__.D'>]
print objects_sorted
# Gives
# [<class '__main__.Definition'>, <class '__main__.A'>, <class
# '__main__.B'>, <class '__main__.C'>, <class '__main__.D'>, <class
# '__main__.E'>]
--
Nick Craig-Wood <[EMAIL PROTECTED]> -- http://www.craig-wood.com/nick
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