Update python-packaging.md

Author: jAniceto

python/python-packaging.md

@@ -36,3 +36,71 @@ setup(
     setup_requires=["setuptools>=62.1.0"],
 )
 ```
+
+## Structure of package with CLI scripts
+
+Example structure:
+
+```
+my_package/
+    my_package/
+        __init__.py
+        cli_scripts.py
+    setup.py
+```
+
+Let's assume your `__init__.py` looks like this (as a side note, I'd recommend moving the classes defined in there to a separate file, and then simply importing that file in the `__init__`):
+
+```python
+class Test(object):
+
+    def __init__(self, a)
+        self.a = a
+
+    def __call__(self):
+        print(self.a)
+```
+
+Now there is an additional file inside the package that utilizes the stuff you implemented in the package, let's call it `cli_scripts.py`:
+
+```python
+import argparse
+
+from my_package import Test
+
+def parse_args():
+    parser = argparse.ArgumentParser()
+    parser.add_argument("a", type=int, help="Just an example argument")
+    return parser.parse_args()
+
+def demonstration():
+    args = parse_args()
+    t = Test(a=args.a)
+    t()
+```
+My suggestion now is to utilize the `console_scripts` entry point inside `setup.py`, which could now look something like this:
+
+```python
+from setuptools import setup
+
+setup(
+    name='testpy',
+    version='0.1',
+    description='Just an example',
+    author='RunOrVeith',
+    author_email='xyz@mailinator.com',
+    packages=["my_package"],
+    entry_points={
+        "console_scripts": ["mypkg=my_package.cli_scripts:demonstration"]},
+    install_requires=[],
+)
+```
+Now when you run `pip install .` inside the top-level `my_package` folder, your package will be installed. The `entry_points` automatically generate an executable for you, that you can now call with the name you gave it inside `setup.py`, in this example `mypkg`. This means you can now run `mypkg 5` and this will call `demonstration()`.
+
+This way:
+
+- you do not need to handle any `__main__` files
+- you can give your script a meaningful name
+- you don't need to care whether your script is executable, or specify to run the script with python
+- you can have as many of these as you want inside the list `entry_points`
+- it forces you to write functions that you could also call from other modules, instead of the `__main__`