Question

Many times I have member functions that copy parameters into object’s fields. For Example:

class NouveauRiches(object):
  def __init__(self, car, mansion, jet, bling):
    self.car = car
    self.mansion = mansion
    self.jet = jet
    self.bling = bling

Is there a python language construct that would make the above code less tedious?
One could use *args:

def __init__(self, *args):
  self.car, self.mansion, self.jet, self.bling = args

+: less tedious

-: function signature not revealing enough. need to dive into function code to know how to use function

-: does not raise a TypeError on call with wrong # of parameters (but does raise a ValueError)

Any other ideas? (Whatever your suggestion, make sure the code calling the function does stays simple)

Answer 1

You could do this with a helper method, something like this:

import inspect

def setargs(func):
    f = inspect.currentframe(1)
    argspec = inspect.getargspec(func)
    for arg in argspec.args:
        setattr(f.f_locals["self"], arg, f.f_locals[arg])

Usage:

class Foo(object):

    def __init__(self, bar, baz=4711):
        setargs(self.__init__)

        print self.bar # Now defined
        print self.baz # Now defined

This is not pretty, and it should probably only be used when prototyping. Please use explicit assignment if you plan to have others read it.

It could probably be improved not to need to take the function as an argument, but that would require even more ugly hacks and trickery 🙂