Python Introspection

Internal

• Python Object-Oriented Programming

Overview

Introspection is Python's equivalent for Java reflection. It is the ability to determine the type of an object at runtime and to dynamically examine Python objects.

Introspect the Members of an Object Instance

All members of an object instance can be identified using inspect.getmembers().

getattr()

getattr() is a built-in function that returns the value of the specified attribute from the specified object. If an attribute with such name does not exist, an AttributeError exception is thrown.

Class Introspection with getattr()

A specific static method can be identified by querying the class attributes with inspect.getmembers() and selecting the matching method, or by name with getattr() builtin.

cls = ...
method_name = 'some_static_method'
try:
  method = getattr(cls, method_name)
  print(method)
except AttributeError:
  print(f"{method_name} method not found in class {cls}")

The inspect Standard Library Module

https://docs.python.org/3/library/inspect.html#module-inspect

inspect is a Standard Library module.

getmembers()

getmembers() returns all members of an object as (name, value) pairs sorted by name. The object can be a module, class, etc. A predicate can be provided to the function, and the function returns only return members that satisfy a given predicate.

Module Introspection with getmembers()

Also see:

Python Language Modularization

Find classes in a module:

import inspect

module = sys.modules['some_package.some_subpackage.SomeClass']
class_tuples = inspect.getmembers(module, inspect.isclass)
for ct in class_tuples:
  print('class name: ', ct[0])
  print('class: ', ct[1])

Invoking Functions and Methods Dynamically

Dynamic Invocation