Different ways to execute python script

With the shebang the script must be located on a volume that permits execution, must be allowed to execute by any security modules, and the interpreter specified in the shebang must be present.

Invoking the interpreter directly only requires the script to be readable.

In general environment they are the same.

However, shebang gives you an extra benefit that you can replace your executable very easily without changing any other files just by substituting the file. The second(better) implementation can potentially be anything. For a script based environment, I always use shebang, with a fixture of languages.

for the shebang line, the argument that you need to be concerned about the location of python binary is not valid. you can always write:

#!/usr/bin/env python

to have local environment to decide for you.

If you are treating python as scripting language that one might execute from a POSIX compliant shell then it really doesn't matter.

That said, given that Python is more or less becoming standardized with its package management and installation, I would argue none of the above. What should be done is that all scripts be turned into callables (either functions or callable class instances) that live within modules (preferably defined a namespace package). That callable is the entry point to your program/script. Then a setuptools compliant setup.py should be placed in the root directory of the project for this module and define that as the entry point to your program.

An example:

In example.package/example/package/script.py:

def main():
    print('hello world')

The setup.py:

from setuptools import setup, find_packages

setup(
    name='example.package',
    description='An example package with an entry point',
    ...
    entry_points="""
    # -*- Entry points: -*-
    [console_scripts]
    script = example.package.script:main
    """,
)

Note that the script is defined to be example.package.script:main, where the element before the : corresponds to the package and the second element is the callable. In this case, it corresponds to the main function in example/package/script.py (standard python module layout).

Installing the package (preferably in a virtualenv) will generate the correct "executable" that will be immediately accessible from the shell, across all operating systems (i.e. on Windows, a script.exe will be created that basically will start Python with the script).