How to import custom python files in app.py

[proneon267]

If I have the following structure inside src directory:
|-->app.py
|-->__init__.py
|-->__main__.py
|-->resources/
|-->assets/
            |-->MyProgram/
                        |-->MyPyFile.py

and I have MyFunc() inside MyFile.py, then how do I import MyFunc() in app.py?

Normally, I could do from assets.MyProgram.MyPyFile import MyFunc, but if I do briefcase dev then it gives error about not finding the assets directory.
I know that I can use self.paths.app of toga.App object but not sure if it is the right way.

[freakboy3742]

You haven't got any __init__.py files on the asset/MyProgram path, so from Python's perspective, assets isn't on the PYTHONPATH. If you add __init__.py files, the path will become importable.

In addition: you say you have this structure "inside your src directory" - but you don't describe whether the path to app.py is src/myapp/app.py or src/app.py. If it's the former (which would be the default structure generated by briefcase new, the import path for MyPyFile.py will be myapp.assets.MyProgram, not assets.MyProgram.

[proneon267]

Yes you are right, the path is src/myapp/app.py. That worked!
Also, if I now have:

|-->assets/
        |-->__init__.py
        |-->MyProgram/
                |-->__init__.py
                |-->MyPyFile.py
                |-->bin/
                        |-->__init__.py
                        |-->Message.txt

In MyPyFile.py, I have:

def Message():
	with open("./bin/Message.txt") as myfile:
		return myfile.read()

Now, if I do briefcase dev then I get error: FileNotFoundError: [Errno 2] No such file or directory: './bin/Message.txt'.
I was thinking of using self.paths.app of toga.App object but that is in app.py. So, how should I reference the files in these cases?

[freakboy3742]

The root of the problem you're seeing is that ./ is a relative path. It depends on the current working directory. That's what paths.app allows you work around - it gives an absolute point in the filesystem to work with.

However, it's difficult to provide a full answer to your question because you're not giving the entire picture. Is assets in your src/myapp folder? Or is it a standalone folder in your project?

If it's in src/myapp, then self.paths.app / "assets" / "bin" / "Message.txt" should return the path you're looking for. If it's a standalone folder, then you'll probably need to use self.paths.app.parent as a root, and also add the assets folder to your sources definition so the extra directory will be copied into your project.

[proneon267]

Hello
Sorry for leaving out the complete directory structure:

.
├── LICENSE
├── logs
│   └── briefcase.2023_03_07-22_51_50.dev.log
├── pyproject.toml
├── README.rst
├── src
│   ├── myapp
│   │   ├── app.py
│   │   ├── assets
│   │   │   ├── __init__.py
│   │   │   ├── MyProgram
│   │   │   │   ├── bin
│   │   │   │   │   ├── __init__.py
│   │   │   │   │   └── Message.txt
│   │   │   │   ├── __init__.py
│   │   │   │   ├── MyPyFile.py
│   │   ├── __init__.py
│   │   ├── __main__.py
│   │   └── resources
│   │       ├── __init__.py
│   │       ├── myapp.icns
│   │       ├── myapp.ico
│   │       └── myapp.png
│   └── myapp.dist-info
│       ├── INSTALLER
│       ├── METADATA
│       ├── top_level.txt
│       └── WHEEL
└── tests
    ├── __init__.py
    ├── myapp.py
    └── test_app.py

13 directories, 29 files

app.py:

"""
My first application
"""
import toga
from toga.style import Pack
from toga.style.pack import COLUMN, ROW
from myapp.assets.MyProgram.MyPyFile import Message

class myapp(toga.App):
	
	def startup(self):
		"""
		Construct and show the Toga application.
		
		Usually, you would add your application to a main content box.
		We then create a main window (with a name matching the app), and
		show the main window.
		"""
		main_box = toga.Box()
		label = toga.Label(text=Message(self.paths.app))
		main_box.add(label)
		self.main_window = toga.MainWindow(title=self.formal_name)
		self.main_window.content = main_box
		self.main_window.show()


def main():
	return myapp()

MyPyFile.py:

import os
def Message(cwd):
	with open(os.path.join(cwd,"assets","MyProgram","bin","Message.txt")) as myfile:
		return myfile.read()

Message.txt:

Hello from Message.txt

The problem is I need self.paths.app in MyPyFile.py but it is accessible only in app.py--- where toga.App object is specified.
For this, I am passing self.paths.app as an argument to the Message() Function in MyPyFile.py. Is this the right way to do this?

[freakboy3742]

It's entirely valid to pass around self.paths.app; it's a Pathlib object, so it's a completely legitimate value to use as an argument. The only thing I can see that is unusual is the use of os.path.join; idiomatic use of Pathlib would be to say:

with (cwd / "assets" / "MyProgram" / "bin" / "Message.txt").open as myfile:

rather than using os.path.join; but otherwise, I can't see any reason it wouldn't work.

[proneon267]

Thanks for helping :)