Gabriel Genellina wrote:
if...elif...else you can use a central registry (a dictionary will do)
and dispatch on the name. Classes act as their own factories.
registry = {}
class Base(object):
kind = "Unknown"
register(Base)
class Gene(Base):
kind = "gene"
def __init__(self, *args, **kw): pass
register(Gene)
class Intron(Base):
kind = "intron"
def __init__(self, *args, **kw): pass
register(Intron)
def register(cls):
registry[cls.kind] = cls
def factory(kind, *args, **kw):
return registry[kind](*args, **kw)
At Thursday 7/12/2006 05:28, Nathan Harmston wrote:
so I was thinking of having a factory class to return the individual
objects for each row......ie
class Factory():
# if passed a gene return a gene object
# if passed an intron return an intron object
# if passed an exom return an exon object
Is this a good way of doing this, or is there a better way to do this
in Python, this is probably the way I d do it in Java.
The basic idea is the same, but instead of a long series ofso I was thinking of having a factory class to return the individual
objects for each row......ie
class Factory():
# if passed a gene return a gene object
# if passed an intron return an intron object
# if passed an exom return an exon object
Is this a good way of doing this, or is there a better way to do this
in Python, this is probably the way I d do it in Java.
if...elif...else you can use a central registry (a dictionary will do)
and dispatch on the name. Classes act as their own factories.
registry = {}
class Base(object):
kind = "Unknown"
register(Base)
class Gene(Base):
kind = "gene"
def __init__(self, *args, **kw): pass
register(Gene)
class Intron(Base):
kind = "intron"
def __init__(self, *args, **kw): pass
register(Intron)
def register(cls):
registry[cls.kind] = cls
def factory(kind, *args, **kw):
return registry[kind](*args, **kw)
register-function called automatically whenever a class is derived from
Base. I also tend to use the class name instead of a separate "kind"
attribute.
registry = {}
class MetaBase(type):
def __init__(cls, name, bases, dict):
registry[name] = cls
class Base(object):
__metaclass__ = MetaBase
class Gene(Base):
def __init__(self, *args, **kw): pass
class Intron(Base):
def __init__(self, *args, **kw): pass
def factory(kind, *args, **kw):
return registry[kind](*args, **kw)
That way you don't have to think about calling the register-function
each time you derive a new class.
Regards,
Jan
