Lachlan Gunn a écrit :
> Hello.
>
> I have a library (SQLObject) that stores data as class variables. I would
> like to set a class variable in a certain context, specific to a certain
> instance of an object. This would require some sort of anonymous class. I
> have attempted to use the following code to set the connection string:
>
> | class SQLStorage:
You probably want:
class SQLStorage(object):
> | def __init__(self, c, debug = False):
> | config = StorageConfiguration(c)
> |
> | connection = sqlobject.connectionForURI(config.databaseString)
> | if debug:
> | connection.debug = True
> |
> | # I don't know whether this is right. My belief is that we can
> | # subclass each table and use _connection on them.
> | class newDatum(DatumTable):
> | _connection = connection
> |
> | class newMetadatum(MetadatumTable):
> | _connection = connection
> |
> | class newChecksum(ChecksumTable):
> | _connection = connection
> |
> | self.__SQLDatum = newDatum
> | self.__SQLMetadatum = newMetadatum
> | self.__SQLChecksum = newChecksum
Are you sure you need name mangling here ?
> This does not work; Python complains that the classes already exist when
> SQLObject is instantiated for a second time. This has led me to try
> instantiating a subclass using DatumTable.__class__ and friends, but this
> requires setting a class name, which, again, limits me to a single
> instance. I *could* have a counter that appends a number to each class
> name, but that's a fairly ugly solution; is it possible to create an
> anonymous class in Python?
Yes. Using type() :
Help on class type in module __builtin__:
class type(object)
| type(object) -> the object's type
| type(name, bases, dict) -> a new type
>>> class Toto(object):
... pass
...
>>> class Tutu(object):
... def __init__(self, what):
... self._toto = type('Autototo', (Toto,), dict(_what=what))
...
>>> t = Tutu(42)
>>> t._toto
<class '__main__.Autototo'>
>>> t._toto._what
42
>>> t._toto()
<__main__.Autototo object at 0xb7c3806c>
>>> t2 = Tutu(1138)
>>> t2._toto
<class '__main__.Autototo'>
>>> t2._toto._what
1138
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