Do packages really require "__init__.py" ?

[denis_beurive]

Hello,

In the official documentation for Python 3 it is written that :

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. In the simplest case, __init__.py can just be an empty file, but it can also execute initialization code for the package or set the __all__ variable, described later.

However, when a create a package without the presence of the file "__init__.py", it "works". I means that Python knows that it is a package even if the file "__init__.py" does not exist.

Demonstration:

Let's consider the following file tree:

├── package
│   ├── __init__.py
│   ├── module1.py
│   ├── module2.py
│   └── module3.py
└── test1.py


And let's consider the following code (the content of the file test1.py):

import os
import sys
from pprint import pformat

sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))

import package
print('What is a package ? %s' %pformat(package))
print('Do packages have a property called "__path__" ? %s' %('yes' if hasattr(package, '__path__') else 'no'))
print('package.__path__ = %s' %package.__path__)
print('')

from package import module1
print('What is a module ? %s' %pformat(module1))
print('Do modules have a property called "__path__" ? %s' %('yes' if hasattr(module1, '__path__') else 'no'))
print('')

Now run the script test1.py:

With the file "package/__init__.py":

Output:
$ ls package/__init__.py && python3 test1.py 
package/__init__.py
What is a package ? <module 'package' from '/home/denis/projects/imap/package_vs_module/package/__init__.py'>
Do packages have a property called "__path__" ? yes
package.__path__ = ['/home/denis/projects/imap/package_vs_module/package']

What is a module ? <module 'package.module1' from '/home/denis/projects/imap/package_vs_module/package/module1.py'>
Do modules have a property called "__path__" ? no

And without the file "package/__init__.py":

Output:
$ rm -f package/__init__.py && rm -rf package/__pycache__ && python3 test1.py 
What is a package ? <module 'package' (namespace)>
Do packages have a property called "__path__" ? yes
package.__path__ = _NamespacePath(['/home/denis/projects/imap/package_vs_module/package', '/home/denis/projects/imap/package_vs_module/package'])

What is a module ? <module 'package.module1' from '/home/denis/projects/imap/package_vs_module/package/module1.py'>
Do modules have a property called "__path__" ? no

Conclusion:

Python recognises "package" as being a package event without the presence of the file "__init__.py".

Do I misunderstand something ?

Thanks,

Denis