Metaprogramming

Metaprogramming#

Metaprogramming is a programming technique where computer programs have the ability to treat other programs as their data. It means that a program can be designed to read, generate, analyze, or transform other programs, and even modify itself while running. In essence, it’s writing code that writes code.

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Let’s take a look at all the core concepts of Metaprogramming.

Program Introspection#

Program introspection allows a program to examine itself during runtime. This includes:

  • Examining variable types

  • Inspecting class hierarchies

  • Analyzing method signatures

  • Accessing documentation strings

  • Exploring code structure

Code Generation#

Code generation involves programs that can write or modify code:

  • Dynamic code evaluation

  • Template metaprogramming

  • Macro systems

  • Source code generation

  • Dynamic proxy creation

Reflection#

Reflection enables programs to modify their structure and behavior at runtime:

  • Dynamic method invocation

  • Runtime class modification

  • Property and method manipulation

  • Dynamic object creation

  • Attribute inspection

Metaprogramming in Python#

Python offers rich metaprogramming capabilities through:

  • Decorators for modifying functions and classes

  • Metaclasses for customizing class creation

  • getattr(), setattr(), and hasattr() for attribute manipulation

  • type() for dynamic type creation

  • eval() and exec() for code evaluation

Example#

# Metaclass example
class MetaLogger(type):
    def __new__(cls, name, bases, attrs):
        # Add logging to all methods
        for key, value in attrs.items():
            if callable(value):
                attrs[key] = cls.log_call(value)
        return super().__new__(cls, name, bases, attrs)

    @staticmethod
    def log_call(func):
        def wrapper(*args, **kwargs):
            print(f"Calling {func.__name__}")
            return func(*args, **kwargs)
        return wrapper

Conclusion#

Metaprogramming is a powerful technique that enables dynamic and flexible program behavior. While it requires careful consideration of maintainability, performance, and security, when properly implemented, it can significantly enhance code reusability and system adaptability.