Behind the Curtain: Using Introspection to Understand Python Objects

There are two main ways to find an object's methods in Python:

1. Using the dir() function:

2. Using the inspect module:

   • Python provides the inspect module for more advanced introspection.

Here's an example:

class MyClass:
  def method1(self):
    print("I'm method 1")

  def method2(self):
    print("I'm method 2")

obj = MyClass()

# Using dir()
print(dir(obj))  # This will print all attributes and methods

# Using inspect
import inspect
methods = inspect.getmembers(obj, inspect.ismethod)
for name, method in methods:
  print(name)  # This will print only method names

Introspection helps write flexible and generic code. For instance, a function can take any object and use dir() or inspect to discover its available methods and call them dynamically.

Using dir():

class MyClass:
  def method1(self):
    print("I'm method 1")

  def method2(self):
    print("I'm method 2")

obj = MyClass()

# Get all attributes and methods using dir()
all_members = dir(obj)

# Print all members (might include non-methods)
print("All members:", all_members)

# You can manually filter methods if needed (not ideal for large lists)
methods = [member for member in all_members if callable(getattr(obj, member))]
print("Methods only (manual filtering):", methods)

Using inspect:

class MyClass:
  def method1(self):
    print("I'm method 1")

  def method2(self):
    print("I'm method 2")

obj = MyClass()

import inspect

# Get all members using inspect.getmembers()
all_members = inspect.getmembers(obj)

# Filter methods using inspect.ismethod()
methods = [member[0] for member in all_members if inspect.ismethod(member[1])]
print("Methods only (using inspect):", methods)

These examples demonstrate both approaches. dir() is simpler but returns everything, while inspect offers more control and filtering capabilities. Choose the method that best suits your needs.

1. IDEs and Interactive Environments:

2. Documentation:

3. Context-Specific Exploration:

Here's a quick example of using hasattr:

class MyClass:
  def method1(self):
    print("I'm method 1")

  def method2(self):
    print("I'm method 2")

obj = MyClass()

# Check if specific methods exist
if hasattr(obj, "method1"):
  obj.method1()

if hasattr(obj, "unknown_method"):
  print("Unknown method doesn't exist")

Remember, dir() and inspect are the core methods for programmatic introspection, but these complementary approaches can be valuable tools during development and exploration.