Python Topics : The __Init__.Py File and Packages
What Is __Init__.Py File in Python?
Python allows users to organize their code into modules and packages which are collections of modules
the __init__.py file is a Python file that is executed when a package is imported
__init__.py is a special file used in Python to define packages and initialize their namespaces
file can contain an initialization code that runs when the package is imported
without this file Python won't recognize a directory as a package
file serves two main purposes
  • marks the directory as a Python package so the interpreter can find the modules inside it
  • it can contain initialization code for the Package
    including importing submodules, defining variables, or executing other code.
Syntax of Importing __Init__.py File
two ways to import a package 
# import the module
import <package_name>.<module_name>

# import specific functions, classes or variables
from <package_name>.<module_name> import <object>
avoid using the '*' operator to import all names from a package/module
it may lead to conflicts and reduce code readability 
from <package_name>.<module_name> import *
Creating a Simple Package Using __init__.py File
create a directory named 'mypackage'
in directory add the modules
  • 'module1.py' containing 'func1'
  • 'module2.py' containing 'func2'
to make it a Python package include an empty 'init.py' file in the 'mypackage' directory
the File structure should appear as 
mypackage
    __init__.py
    module1.py
    module2.py
main.py
__init__.py is an empty file

module1.py code 

# Define a function called func1
def func1():
    print("This is func1 from module1")
module2.py code 
# Define a function called func2
def func2():
    print("This is func2 from module2")
below the __all__ variable is a list of strings that indicate the names that should be imported when using the * operator
the dot operator (.) before the module names means that they are relative imports (imported from the same package) 
# Define the __all__ variable
__all__ = ["module1", "module2"]

# Import the submodules
from . import module1
from . import module2
main.py is the 'mule' 
# Import the package
import mypackage

# Import the modules
import mypackage.module1
import mypackage.module2

# Call the functions
mypackage.module1.func1()
mypackage.module2.func2()
Package Import Optimization Using __init__.py File
a better main.py 
# main.py
# Import specific modules instead of using *
from mypackage import module1, module2

# Call the functions
module1.func1()
module2.func2()
Define Variables and Execute Code in __init__.py file
if there is a need to initialize variables or execute code when a package is imported, it can be done in the __init__.py file
below the welcome message is printed whae the module is imported 
# Define a variable called version
version = "1.0.0"

# Print a welcome message
print(f"Welcome to mypackage version {version}")
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