Create classes at runtnime

Marc Aymerich glicerinu at
Sat Feb 5 17:47:05 CET 2011

On Feb 5, 1:06 pm, Marc Aymerich <glicer... at> wrote:
> Thank you all for the answers!
> I'll try to give you the context in which I need to generate classes
> like this.
> I'm developing a reusable control panel for an ISP. I have several
> modules (VirtualUser, SystemUser, VPS, VirtualHost, ...) and they all
> share the fact that you can have limits on resource consumption. for
> example.
> VPS: has limits on swap, memory, cpu and disk.
> SystemUser: has limits on disk and traffic.
> As all modules share this property of being limited I have decided to
> split the limit functionality in a separate module (called resources).
> Resources are associated dinamically with (vps, systemuser ...)
> through a Monitor class. So it's up to you decide what limits you are
> interested to put in the VPS or in the SystemUser ...
> So when you attach the "disk limit" to SystemUser model is necessary
> to create a web form for SystemUser a bit different than if you decide
> to have disk and traffic limits. That is what my posted code is
> supposed to do.
> Do you think that I am on the wrong way designing the control panel
> like this?
> Btw, I've seen several interesting ideas to create the class
> dinamically (with class factorys, MetaClass, dictionaries ..), but I
> have not yet clear whether this will be usefull for create the
> __init__ function at runtime too. Any clue on this?

this seems to work :)

def makeLimitForm(name, monitors, _model):

    class Meta:
        model = _model
    dct = { 'Meta': Meta }

    for monitor in monitors:
        field_name = monitor.resource + "_limit"
        dct[field_name] = forms.CharField(max_length=100,

    def __init__(self, *args, **kwargs):
        ModelForm.__init__(self, *args, **kwargs)
        if 'instance' in kwargs:
            for monitor in monitors:
                field_name = monitor.resource + "_limit"
                print monitor
                self.fields[field_name].initial =

    dct['__init__'] = __init__

    return type(name,(ModelForm,),dct)

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