Python Import and package with sample

This article will cover 4 Cases of Import:

1. Everything from module in package

2. Certain functions from py file in package

3. py file at same level (relative import)

4. using __all__ with import *

Create a folder structure as below

first_pkg is the module to import , there are 2 services inside and 1 lib file . all __init__.py are empty

import everything from service1 but only api1 and api2

service1.py
def api1():
    print('api1')
def api2():
    print('api2')
def internal():
    print('internal func')
__all__ = ["api1","api2"]

first_pkg_test.py
from first_pkg.api.service1 import *
if __name__ == “__main__”:
    api1()
    api2()
    #internal() #this will throw error

Import certain functions from service2 and lib

service2.py
def api3():
    print('api3')

first_pkg_test.py
import first_pkg.api.service2 as service2
if __name__ == "__main__":
    service2.api3()

lib.py
def lib1():
    print('lib1')

first_pkg_test.py
import first_pkg.lib as lib
if __name__ == "__main__":
    lib.lib1()

Import same level py file

first_pkg_lib.py
def pkg_lib_outside():
    print('pkg lib outside')

first_pkg_test.py
from first_pkg_lib import pkg_lib_outside
if __name__ == "__main__":
    pkg_lib_outside()

Consolidate everything into package level export and import *

__init__.py file (under first_pkg) :

from .lib import lib1
from .api.service1 import api1, api2
from .api.service2 import api3
__all__ = ['lib1','api1','api2','api3']

In first_pkg_test.py
from first_pkg import *
if __name__ == "__main__":
lib1()
api1()
api2()
api3()

Make module executable from python command

add __main__.py in first_pkg folder .

Load modules by string name

In __main__.py , we can load some modules by passing string name . this could be useful when the module name is dynamically computed

print('package1 loaded')
import importlib
service = importlib.import_module('api.service1')
service.api1()

Now run the package

Python3 first_pkg