Entry

How can I create an object instance giving its classname at runtime?

Feb 11th, 2008 19:28
Gabriel, unknown unknown, Nathan Wallace, Alex, Emile van Sebille, Manus Hand, Michal Wallace

This sort of thing works:

>>> class C: pass
... 
>>> c = eval ('C') ()
>>> c
<__main__.C instance at 103e18>
>>> 

-----OR TRY-----

You could also play with changing the instance's class or bases
attributes, e.g.:

>>> class T1:
        def __repr__(self):
                return "T1"
        
>>> class P1:
        def __repr__(self):
                return "P1"
        
>>> a = P1()
>>> a
P1
>>> a.__class__ = T1
>>> a
T1

--- or try things like:

>>> class T3:
        def __str__(self):
                return "T3"

>>> a.__class__.__bases__=(T3,)
>>> a
T1
>>> print a
T3

----OR TRY----

After dynamically realizing that "object" should be an instance of a 
particular "className" found in a certain "moduleName":

code = __import__(moduleName)
object = getattr(code, className)(initParam1, initParam2, etc.)

----OR TRY----

    >>> class C:
    ...    pass
    ...
    >>> def makeNew(className):
    ...     return globals()[className]()
    ...
    >>> makeNew('C')
    <__main__.C instance at 80dac50>