Question

I want determine the type of an attribute in a class. I am using setattr to set the value, and I would like to check the type that is expected, so that I can properly convert a string value before calling setattr.

How do you do this in python?

EDIT 1-
Some additional information based on the answers so far:

I only know the name of the property that I want the type for, here is some code:

def populate_object_properties(values_as_strings, 
                               object_to_populate, 
                               properties_to_populate):
    for k in properties_to_populate:        
        value = values_as_strings.get(k)
        if value:
            setattr(object_to_populate, k, value)
        else:
            setattr(object_to_populate, k, None)

I want to be able test that value is the right type before I call setattr.

Edit 2- The reason why I need to validate the type, is that I’m using Google AppEngine’s db.Model as the base type for the object_to_populate, and it doesn’t like when a put a string into an int type. I was trying to keep the question as simple as possible, but maybe that piece of information makes a difference in how someone would answer.(?)

Answer 1

In AppEngine, each model has a properties() class method, which returns the dict of properties you declared in your model. You can use it to check the types your model expects for each attribute:

def populate_object_properties(values_as_strings, 
                               object_to_populate, 
                               properties_to_populate):
    model_properties = object_to_populate.properties()
    for k in properties_to_populate:        
        value = values_as_strings.get(k)
        model_property = model_properties.get(k)
        if value:
            if isinstance(model_property, StringProperty):
                setattr(object_to_populate, k, str(value))
            elif isinstance(model_property, IntegerProperty):
                setattr(object_to_populate, k, int(value))
        else:
            setattr(object_to_populate, k, None)