How Can I Type Hint a Method's Enclosing Class in Python?

Type Hinting a Method with Enclosing Class Type

In Python, representing the type of a method's enclosing class can be achieved through various methods depending on the Python version.

Python 3.7 with 'from future import annotations'

By enabling the "deferred evaluation of annotations" feature with from __future__ import annotations, annotations can be stored as strings and evaluated asynchronously.

from __future__ import annotations

class Position:
    def __add__(self, other: 'Position') -> 'Position':
        ...

Python 3.11 with 'from typing import Self'

Python 3.11 introduces the Self type to represent the enclosing class type.

from typing import Self

class Position:
    def __add__(self, other: Self) -> Self:
        ...

Python <3.7

For Python versions prior to 3.7, strings are used to indicate the enclosing class type.

class Position:
    def __add__(self, other: 'Position') -> 'Position':
        ...<p><strong>Handling Forward References</strong></p>
<p>PEP 484 specifies that forward references should be represented as strings until they are fully defined.</p>
<pre class="brush:php;toolbar:false">class Tree:
    def __init__(self, left: 'Tree', right: 'Tree'):
        ...

Alternatives

Avoid using dummy definitions of the enclosing class or monkey-patching the class to add annotations, as these approaches may result in incorrect annotation behavior.

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