Initialize all the classes in a module into namele

问题:

Is there a way to initialize all classes from a python module into a list of nameless objects?

Example I have a module rules which contains all child classes from a class Rule. Because of that, I'm certain they will all implement a method run() and will have a attribute name which will be generated during the call of __init__

I would like to have a list of objects dynamically initiated from those classes. By dynamically initialized i mean that they don't have to be named explicitly.

The questions are:

Is it possible to iterate through all classes in a module?

Can a nameless object be initiated?

回答1:

There are at least two approaches you can take. You can get all of the subclasses of a class by calling a class's __subclasses__() method. So if your parent class is called Rule, you could call:

rule_list = [cls() for cls in Rule.__subclasses__()]

This will give you all subclasses of Rule, and will not limit them to the ones found in a particular module.

If you have a handle to your module, you can iterate over its content. Like so:

import rule
rule_list = []
for name in dir(rule):
    value = getattr(rule, name)
    if isinstance(value, type) and issubclass(value, Rule):
        rule_list.append(value())

Unfortunately, issubclass throws TypeError if you give it an object that is not a class as its first argument. So you have to handle that somehow.

EDIT: dealing with the issubclass quirk per @Blckknght's suggestion.