How does __init__.py work?

Question

Python

Quoting the documentation: https://docs.python.org/3/tutorial/modules.html#pa...

The __init__.py files are required to make Python treat the directories as containing packages; this is done to prevent directories with a common name, such as string, from unintentionally hiding valid modules that occur later on the module search path

Let's say in one directory from sys.path there is a package1 folder . Its structure:

package1/
     sub_package1/
          module1.py
     sub_package2/
          module2.py

Next, in the interpreter, I write import package1. Why can't you just find the package1 folder and import it without __init__.py? (i.e. why is it not clear to python that a folder with modules and with the correct name is a package that needs to be imported?) Can you give an example of prevent directories with a common name, such as string, from unintentionally hiding valid modules or when is __init__.py useful?

Answer 1

1. Python can search for modules in several folders in order of priority (including paths in PYTHON_PATH).
2. Imagine that on one of the paths you have this:
and on the other, like this:
3. You import the string module, but the directory with the string folder is processed first. And you have, for example, not a Python code at all, but some kind of documentation. You actually want to import string.py from the second folder, but the interpreter will think that you need to take the directory, and will give an error (saying that they say this is not a valid package or something like that).
4. To prevent this from happening, the developers decided that you should explicitly mark that you want the folder to be considered a package. This is the same as marking files with python code with the .py extension - you don't expect the interpreter to treat .txt files as python modules, do you? The same goes for the folder.
Well, yes, as Vyacheslav already mentioned , __init__.py does not have to be empty at all, for example, there may be re-exports.

Answer 2

After re-reading the comments, I think that the correct answer is:
yes, because the developers decided to do just that, they decided to make this file a package marker ... and now everyone is used to
it just like curly braces, begin / end, semicolons in other languages. .. without which the python does, but what prevents other languages? for the same reason

Answer 3

If there is no __init__.py in the folder, then it is not a package.
Roughly speaking, __init__.py is needed in order to be able to load exactly the package and the package operation model to function.

import package1
from package1.sub_package1 import *

Answer 4

Since Python 3.3+ . This file is no longer needed.