Dynamically creating classes - Python

问题:

I need to dynamically create a class. To go in futher detail I need to dynamically create a subclass of Django's Form class.

By "dynamically" I intend to create a class based on configuration provided by a user.

---

e.g.

I want a class named CommentForm which should subclass the Form class.

The class should have a list of chosen attributes.

....in this case

name = forms.CharField()
comment = forms.CharField(widget=forms.Textarea())

---

Any useful tips? :)

回答1:

You can create classes on the fly by calling the type built-in, passing appropriate arguments along, like:

CommentForm = type("CommentForm", (Form,), { 
    'name': forms.CharField(),
    ...
})

It works with new-style classes. I am not sure, whether this would also work with old-style classes.

回答2:

Classes can be defined almost anywhere.

def newclass(val):
  class C(object):
    def __str__(self):
      return str(val)
  return C

MyClass = newclass(5)
m = MyClass()
print str(m)