How to Type Hint in Python Without Importing a Library?

0
0
Asked By CuriousCoder42 On

I'm working on a project where I'm using Celery, and I've made some utility functions that build and return task signatures. There have been times when I've used these utility functions in places where I haven't actually imported the Celery task type. What's the best practice according to Python's PEP 8 for handling this? It feels a bit excessive to import a whole library just for a type hint, but I'd like to keep my type hints without resorting to a generic `-> Object`. Any advice?

4 Answers

Answered By Pythonista101 On

You should check out Python's `TYPE_CHECKING`. It's designed for this scenario!

You can use it like this:

```python
from typing import TYPE_CHECKING

if TYPE_CHECKING:
from somelib import SomeType
```

And remember, libraries are cached globally in Python, so importing a library multiple times doesn't add runtime costs as long as you import it in the same way.

Answered By TypeHintGuru21 On

You can utilize `if TYPE_CHECKING:` to import your type hints.

```python
from typing import TYPE_CHECKING

if TYPE_CHECKING:
from somelib import SomeType
```

This approach allows you to import types only during type checking, and when you reference them, just wrap the type in quotes like this:

```python
def func(x: 'SomeType'):
```

This helps avoid unnecessary imports at runtime, which is nice since it keeps your code clean and efficient!

Answered By DevDude99 On

Definitely check the Python docs for `TYPE_CHECKING`. It lays out all the information you might need for type hints without the performance hit of an import. It’s a lifesaver for keeping your code clean!

Answered By CodeWhisperer88 On

I get where you're coming from, but why not just import the type directly? Like this:

```python
from somelib import SomeType
```

It's not too heavy if you're already importing the library in other parts of your code. Just keep in mind that importing can load a lot of code, especially if you're not using it in your function.

Related Questions

LEAVE A REPLY

Please enter your comment!
Please enter your name here

This site uses Akismet to reduce spam. Learn how your comment data is processed.