Can You Monkey Patch Core Type Methods in Python?

Can Python Monkey Patch Core Type Methods?

In Python, monkey patching involves modifying the behavior of an existing class or object at runtime. However, extending core types like ints or floats is not permitted in Python. This raises questions about the underlying reasons and potential alternatives.

The core difference lies in the immutability of data in Python. All built-in classes and methods defined in C extensions are immutable to ensure data integrity across interpreters within the same process. Monkeypatching such data would impact unrelated interpreters, leading to unexpected behavior.

In contrast, classes defined in Python code can be monkeypatched because they reside within the local interpreter and do not pose the same immutability concerns. Therefore, extending user-defined classes through monkey patching is feasible in Python.

For example, a user-defined class called Item can be monkey-patched to include a method called should_equal for testing purposes. This can improve readability by streamlining the testing syntax:

<code class="python"># Before monkey patching
assert_equal(item.price, 19.99)

# After monkey patching
item.price.should_equal(19.99)</code>

While Python does not allow monkey patching of core types like Ruby, it provides the flexibility to extend user-defined classes through this technique, cater to specific testing and readability requirements.

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