stackoverflow.com › questions › 33045222 › how-do-you-alias-a-type-in-python

Python 3.5+

Since Python 3.5 you may use typing module.

Quoting docs, A type alias is defined by assigning the type to the alias:

Copy# Python 3.5-3.8
from typing import List
Vector = List[float]

# Python 3.9+
Vector = list[float] # No import needed, lower case l

To learn more about enforcing types in Python you may want to get familiar with PEPs: PEP483 and PEP484.

Python historically was using duck-typing instead of strong typing and hadn't built-in way of declaring types before 3.5 release.

Answer from Łukasz Rogalski on Stack Overflow

GitHub

gist.github.com › simonwhitaker › 3a24d669b26b4f373690c6eb113c3ae7

python-type-alias-vs-newtype.md · GitHub

Type aliases are exactly that; simply an alias for a type. Anywhere you refer to the original type (e.g. list[float]), you can now also refer to it as the alias (e.g.

Stack Overflow

stackoverflow.com › questions › 33045222 › how-do-you-alias-a-type-in-python

How do you alias a type in Python? - Stack Overflow

Python 3.5+

Since Python 3.5 you may use typing module.

Quoting docs, A type alias is defined by assigning the type to the alias:

Copy# Python 3.5-3.8
from typing import List
Vector = List[float]

# Python 3.9+
Vector = list[float] # No import needed, lower case l

To learn more about enforcing types in Python you may want to get familiar with PEPs: PEP483 and PEP484.

Python historically was using duck-typing instead of strong typing and hadn't built-in way of declaring types before 3.5 release.

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Python 3.10+

Since Python 3.10, the TypeAlias annotation is available in the typing module.

It is used to explicitly indicate that the assignment is done to generate a type alias. For example:

CopyPoint: TypeAlias = tuple[float, float]
Triangle: TypeAlias = tuple[Point, Point, Point]

You can read more about the TypeAlias annotation on the PEP 613 that introduced it.

Discussions

Static Enforced Non generic Type alias?

From the pep 484, we have this code (now modernized): type Url = str def retry(url: Url, retry_count: int) -> None: ... But I didn´t find any reference of this aliases should/ are enforced in static analysis. for instance i expect: test: str = 'not_an_url' smght = retry(test) # warning test ... More on discuss.python.org

discuss.python.org

0

February 6, 2024

Docstrings for new type aliases as defined in PEP 695 - Typing - Discussions on Python.org

Today I’ve started updating to Python 3.12 and adapted my code base to use the new typing aliases defined in PEP 695. Previously, my type was defined as CustomType = dict[str, int] with a docstring below using multine strings. Using the new type alias syntax, this was converted to type CustomType ... More on discuss.python.org

discuss.python.org

2

October 12, 2023

Help understanding Type Aliases

For the most part, there isn't much of a difference, although the newer syntax should be preferred if you don't plan to support older versions of Python. Basically, type Vector = list[float] is a newer way to write from typing import TypeAlias Vector: TypeAlias = list[float] and for the most part type analysis tools treat Vector = list[float] the same, despite technically containing different types. I think Mypy's documentation explains it better than I can: https://mypy.readthedocs.io/en/stable/kinds_of_types.html#type-aliases More on reddit.com

r/learnpython

2

3

April 28, 2025

Naming convention for type aliases

The very first example here: https://docs.python.org/3/library/typing.html#type-aliases More on reddit.com

r/Python

13

8

April 2, 2022

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