Get number of args for function

Question

I have a module, ui. I'd like to get a list of all the classes that ui defines which are a subclass of ui.View, and that can be called without arguments.

I've tried the following code:

ui_elements=[d for d in ui.__dict__.values() if type(d)==type and inspect.getargspec(d.__init__)[0]==1 and isinstance(d(),ui.View)]

But I get the following error from inside the inspect module:

TypeError: <slot wrapper '__init__' of 'object' objects> is not a Python function

I'm using inspect instead of a try: except: just because checking beforehand seems like a better solution than trying it to see if it works.

So, how can I get a list of all the classes that subclass ui.View and do not require arguments to create? I'd like to do this inline if possible, and I'd also like to avoid using try:/except: statements.

Answer 1

To get a list comprehension with try/except you can use a local function:

def tryCreate(class_):
  try:
    return class_()
  except:
    return None

ui_elements = set(tryCreate(d) for d in ui.__dict__.values()
    if issubclass(d, ui.View)) - set(None)

Okay, it's a set comprehension in the end ;-)