Módulo record

[Rasta Popoulus]

El módulo record que he utilizado en el ejercicio de listas, tal como nos 
pone en la descripción se emplea para simular registros o algo así, les dejo 
el código entero copiado aqui porq no se donde puedo dejar el archivo si 
alguien lo quiere lo envio sin problema.
Por cierto ,me imagino que estareis enterados del ENTORNO GRÁFICO 
desarrollado para python, llamado Python G, por la Universidad de Castelló 
Jaume I, no?? Por si de caso:
http://www3.uji.es/~dllorens/PythonG/

El codigo de record:
import warnings

class metaMetaBunch(type):
  # metaclass for new and improved "Bunch": implicitly defines 
\texttt{__}\emph{slots}\texttt{__}, \texttt{__}\emph{init}\texttt{__} and 
\texttt{__}\emph{repr}\texttt{__}
  # from variables bound in class scope. An instance of \emph{metaMetaBunch} 
(a class whose metaclass
  # is \emph{metaMetaBunch}) defines only class-scope variables (and 
possibly special methods, but
  # NOT \texttt{__}\emph{init}\texttt{__} and 
\texttt{__}\emph{repr}\texttt{__}!).  \emph{metaMetaBunch} removes those 
variables from class scope,
  # snuggles them instead as items in a class-scope dict named 
\texttt{__}\emph{dflts}\texttt{__}, and puts in the class a
  #  \texttt{__}\emph{slots}\texttt{__} listing those variables' names, an 
\texttt{__}\emph{init}\texttt{__} that takes as optional keyword
  # arguments each of them (using the values in 
\texttt{__}\emph{dflts}\texttt{__} as defaults for missing ones), and
  # a \texttt{__}\emph{repr}\texttt{__} that shows the repr of each 
attribute that differs from its default value (the output
  # of \texttt{__}\emph{repr}\texttt{__} can be passed to 
\texttt{__}\emph{eval}\texttt{__} to make an equal instance, as per the 
usual convention
  # in the matter).

  def __new__(cls, classname, bases, classdict):
    # Everything needs to be done in \texttt{__}\emph{new}\texttt{__}, since 
type.\texttt{__}\emph{new}\texttt{__} is where 
\texttt{__}\emph{slots}\texttt{__} are taken
    # into account.

    # Define as local functions the \texttt{__}\emph{init}\texttt{__} and 
\texttt{__}\emph{repr}\texttt{__} that we'll use in the new class.

    def __init__(self, **kw):
      # Simplistic \texttt{__}\emph{init}\texttt{__}: first set all 
attributes to default values, then override those explicitly
      # passed in \emph{kw}.

      for k in self.__dflts__: setattr(self, k, self.__dflts__[k])
      for k in kw: setattr(self, k, kw[k])

    def __repr__(self):
      # Clever \texttt{__}\emph{repr}\texttt{__}: show only attributes that 
differ from the respective default values,
      # for compactness.

      rep = [ '%s=%r' % (k, getattr(self, k)) for k in self.__dflts__
              if getattr(self, k) != self.__dflts__[k]]
      return '%s(%s)' % (classname, ', '.join(rep))

    # Build the newdict that we'll use as class-dict for the new class
    newdict = {'__slots__':[], '__dflts__':{}, '__init__':__init__, 
'__repr__':__repr__}

    for k in classdict:
      if k.startswith('__'):
        # Special methods: copy to \emph{newdict}, warn about conflicts.
        if k in newdict:
          warnings.warn("Can't set attr %r in bunch-class %r" % (k, 
classname))
        else:
          newdict[k] = classdict[k]
      else:
        # Class variables, store name in \texttt{__}\emph{slots}\texttt{__} 
and name and value as an item in \texttt{__}\emph{dflts}\texttt{__}.
        newdict['__slots__'].append(k)
        newdict['__dflts__'][k] = classdict[k]
    # Finally delegate the rest of the work to 
\emph{type}.\texttt{__}\emph{new}\texttt{__}
    return type.__new__(cls, classname, bases, newdict)

class record(object):
  # For convenience: inheriting from \emph{record} can be used to get the 
new metaclass (same as
  # defining \texttt{__}\emph{metaclass}\texttt{__} yourself).
  __metaclass__ = metaMetaBunch


if __name__ == "__main__":
  # Example use: a \emph{record} class.
  class Point(record):
    # A point has $x$ and $y$ coordinates, defaulting to 0.0, and a color, 
defaulting to \texttt{'gray'} -- and
    # nothing more, except what Python and the metaclass conspire to add, 
such as \texttt{__}\emph{init}\texttt{__}
    # and \texttt{__}\emph{repr}\texttt{__}.
    x = 0.0
    y = 0.0
    color = 'gray'

  # Example uses of class \emph{Point}.
  q = Point()
  print q

  p = Point(x=1.2, y=3.4)
  print p

  r = Point(x=2.0, color='blue')
  print r
  print r.x, r.y

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