How to create a Python extension with multiple files?

[sk-uma]

Hi! Thanks for the great project.

I'm trying to create a Python package using Codon. I've written a small example that uses multiple files, but I'm confused about how to build it correctly.

Here's my file structure:

mymodule/
├── __init__.py
└── main.py
setup.py

__init__.py

from .main import MyClass, ack
print("Hello, Codon! in __init__.py")

main.py

print("Hello, Codon! in main.py")

@dataclass(python=True)
class MyClass:
    def __init__(self):
        print("MyClass initialized")

    def say_hello(self):
        print("Hello, Codon!")

def ack(m: int, n: int) -> int:
    if m == 0:
        return n + 1
    elif n == 0:
        return ack(m - 1, 1)
    else:
        return ack(m - 1, ack(m, n - 1))

I followed the documentation and created a setup.py that builds the extension using Codon.
However, when I try to import MyClass or ack, I get an ImportError. It seems that only the file specified in the extension (__init__.py) is being compiled.

What's the proper way to build a Codon-based Python extension that includes multiple files?

The full example is here:
👉 https://github.com/sk-uma/codon-pyext-example

Thanks in advance for any help!

[elisbyberi]

Make sure not to run test.py in the same folder as the uncompiled Codon mymodule module.

Your example works:

# test.py
import mymodule

Result:

Hello, Codon! in main.py
Hello, Codon! in __init__.py

[sk-uma]

@elisbyberi

Thank you!

Do you know how to import the functions and classes defined in main.py?
As shown in the standard output, main.py is being executed, but when I try to import ack or MyClass, I get an error like this:

>>> from mymodule import ack
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: cannot import name 'ack' from 'mymodule'

[elisbyberi]

ImportError: cannot import name 'ack' from 'mymodule'

You’ve exposed MyClass and ack in __init__.py, but the file doesn’t actually export any class definitions or functions. In a well-structured modular design, nested modules should remain encapsulated.

Python intentionally avoids enforcing such constraints, following its ‘we’re all consenting adults’ philosophy. However, Codon’s static nature makes this approach a poor fit—we should prioritize explicit encapsulation.

[sk-uma]

Thank you, this helped me understand Codon better.
I'll consolidate the public functions into __init__.py.