lz-import 0.1.0

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Lazy Import

Usage

# File: company.py
from user import User

class Company:
    name = "company"

    def get_user(self) -> User:
        return User()

# File: user.py
from company import Company

class User:
    name = "user"

    def get_company(self) -> Company:
        return Company()

if __name__ == "__main__":
    company = User.get_company()

This file layout will throw a circular import error, but if we can do a lazy import, it's perfectly fine. Just wrap the block of code like follow snippets.

from lazy_import import lazy_import

with lazy_import():
    from user import User

...

User will be imported when the __call__ or __getattr__ methods are called.
This example codes are implemented in the tests folder. See tests/test_user.py and tests/test_company.py.

NOTE

Keep in mind that the class of lazy imported is not the same class with your original User class. It is wrapped by another class inside of lazy_imported(). Also, this library works with mypy.

TODO

This library currently doesn't support follow syntax:

with lazy_import():
    # these are actually possible but currently not implmented...
    import user  
    from user import User as user

How it works?

We can find out which files to import by parsing bytecodes inside the with syntax. After that, just wrap the value to be imported.