Python is a dynamically typed language, which means that the data type of a variable is determined at runtime. While this provides flexibility, it can also make code harder to understand and maintain. Type hints are a way to specify the expected types of function arguments and return values, making it easier to reason about the code and catch potential errors before runtime.

Recursive type hints, in particular, are a powerful tool when it comes to defining complex data structures in Python, especially in Object-Oriented Programming (OOP). Recursive data structures are those that contain references to themselves, such as trees, graphs, and linked lists. Recursive type hints allow us to specify these complex data structures in a way that is both readable and maintainable.

The typing module, introduced in Python 3.5, provides a way to define complex types, such as lists, tuples, and dictionaries. It also provides a way to define recursive types using forward references. Forward references allow us to refer to a class that has not yet been defined, which is necessary when defining a class that contains references to itself.

Here's an example of a recursive type hint for a binary tree:

from typing import List, Optional

class Node:
    def __init__(self, value: int, left: Optional['Node'] = None, right: Optional['Node'] = None):
        self.value = value
        self.left = left
        self.right = right

Tree = Optional[Node]

In this example, we define a Node class that has a value attribute, as well as left and right child nodes. We use the Optional type hint to indicate that the left and right child nodes can be None. We also use the forward reference notation to refer to the Node class itself inside the class definition. Finally, we define a Tree type hint as an Optional['Node'], indicating that a tree can be either a Node or None. Using this recursive type hint, we can define a binary tree as follows:

tree = Node(
    1,
    left=Node(
        2,
        left=Node(4),
        right=Node(5),
    ),
    right=Node(
        3,
        left=Node(6),
        right=Node(7),
    ),
)

In conclusion, recursive type hints are a powerful feature of Python that can help make code more readable and maintainable, especially when it comes to defining complex data structures in OOP. By using the typing module and forward references, we can define types that contain themselves, such as trees and graphs, with ease.