How can you set class attributes from variable arguments (kwargs) in python

Question

Suppose I have a class with a constructor (or other function) that takes a variable number of arguments and then sets them as class attributes conditionally.

I could set them manually, but it seems that variable parameters are common enough in python that there should be a common idiom for doing this. But I'm not sure how to do this dynamically.

I have an example using eval, but that's hardly safe. I want to know the proper way to do this -- maybe with lambda?

class Foo:     def setAllManually(self, a=None, b=None, c=None):         if a!=None:              self.a = a         if b!=None:             self.b = b         if c!=None:             self.c = c     def setAllWithEval(self, **kwargs):         for key in **kwargs:             if kwargs[param] != None                 eval("self." + key + "=" + kwargs[param]) 

Answer 1

You could update the __dict__ attribute (which represents the instance attributes in the form of a dictionary) with the keyword arguments:

class Bar(object):     def __init__(self, **kwargs):         self.__dict__.update(kwargs) 

then you can:

>>> bar = Bar(a=1, b=2) >>> bar.a 1 

and with something like:

allowed_keys = {'a', 'b', 'c'} self.__dict__.update((k, v) for k, v in kwargs.items() if k in allowed_keys) 

you could filter the keys beforehand (use iteritems instead of items if you’re still using Python 2.x).