Reflection and Introspection in Python

1. Introduction

Reflection and introspection in Python are powerful features that allow developers to examine and manipulate objects at runtime. This lesson covers the definitions, key concepts, and practical examples to enhance your understanding of these capabilities.

2. Key Concepts

• Reflection: The ability of a program to examine its own structure and behavior.
• Introspection: The ability to determine the type or properties of an object at runtime.

3. Reflection

Reflection involves examining and modifying the properties and behaviors of objects. In Python, this can be achieved using the built-in functions and the inspect module.

import inspect

class Sample:
    def method(self):
        return "method called"

sample = Sample()
methods = inspect.getmembers(sample, predicate=inspect.ismethod)
print(methods)  # Outputs all methods of the sample instance
                

In the example above, we use inspect.getmembers to retrieve all methods of the Sample class instance.

4. Introspection

Introspection allows you to examine the type or properties of an object. Common functions used for introspection include type(), dir(), and isinstance().

sample = Sample()
print(type(sample))  # Outputs: <class '__main__.Sample'>
print(dir(sample))   # Outputs attributes and methods of the sample instance
print(isinstance(sample, Sample))  # Outputs: True
                

Using these functions, you can gather information about the objects you are working with, which can be helpful for debugging and dynamic behavior.

5. Best Practices

• Use reflection and introspection sparingly to avoid complexity.
• Document your code to clarify when and why reflection is used.
• Test extensively to ensure that dynamic behavior does not introduce bugs.

6. FAQ