Python - why can I import modules without __init__.py at all?

Question

I'm new to Python and I still can't get my head around why we need a __init__.py file to import modules. I have gone through other questions and answers, such as this.

What confuses me is that I can import my modules without __init__py, so why do I need it at all?

My example,

index.py    modules/       hello/           hello.py           HelloWorld.py 

index.py,

import os import sys  root = os.path.dirname(__file__) sys.path.append(root + "/modules/hello")  # IMPORTS MODULES from hello import hello from HelloWorld import HelloWorld  def application(environ, start_response):      results = []      results.append(hello())      helloWorld = HelloWorld()     results.append(helloWorld.sayHello())      output = "<br/>".join(results)      response_body = output      status = '200 OK'      response_headers = [('Content-Type', 'text/html'),                        ('Content-Length', str(len(response_body)))]      start_response(status, response_headers)      return [response_body] 

modules/hello/hello.py,

def hello():     return 'Hello World from hello.py!' 

modules/hello/HelloWorld.py,

# define a class class HelloWorld:     def __init__(self):         self.message = 'Hello World from HelloWorld.py!'      def sayHello(self):         return self.message 

Result,

Hello World from hello.py! Hello World from HelloWorld.py! 

What it takes is just these two lines,

root = os.path.dirname(__file__) sys.path.append(root + "/modules/hello") 

Without any of __init__py. Can someone explain why it works in this way?

If __init__py is the proper way, what should I do/change in my code?

Answer 1

Based on this link: Since Python 3.3

Allowing implicit namespace packages means that the requirement to provide an __init__.py file can be dropped completely

Answer 2

__init__.py is for packages. A package contains a collection of related modules. If you just have a single module you want to use, you don't need to use __init__.py; just put the single .py file somewhere on the system path and you can import it.

The purpose of packages is not just to allow you to import the modules inside them. It's to group the modules together. The main benefit of this is that, if a module is inside a package, then that module can import other modules from the package using relative imports. If you have foo.py and bar.py in the same package, then foo can just do from . import bar. This makes intra-package imports more compact and easier to reorganize if you restructure the package or change its name.

Also, an obvious benefit is. . . if you make it a package, you don't have to do that sys.path stuff every time you want to import something from it.