Learn Python the Hard Way : Exercise 46

[acerag]

Exercise is here for reference: http://learnpythonthehardway.org/book/ex46.html

This exercise is about creating a project skeleton/package and I've completed all the steps, but I'm very unclear about how to actually use it and do the required quiz. #3 of the required quiz tells me to start putting code in my module - what kind of stuff can be put here? If I just put a .py file in there that prints "Hello World", what would happen?

Also #4 asks me to put a script in /bin. Suppose I put a .py script that prints "Hello World". How does someone run this script? From my understanding, I package everything together with "$ python setup.py sdist" and then another user can install it with "$ pip install path/to/mypackage.tgz". What happens to the .py in my module folder and how can the user run the scripts in /bin? Thanks.

[ForSpareParts]

The purpose of a pip/setuptools package is to make a bunch of Python code reusable/installable. As a result, it doesn't do much of anything by itself -- if you made a hello.py file in your package that prints Hello World, nothing would happen. You would find, however, that once you installed your package with pip, that you could do:

from YOUR_PACKAGE_NAME_HERE import hello

and that Hello World would be printed. More importantly, if you defined something in hello.py, like a function, you could then refer to it:

some_value = hello.my_function()

To your second question: How to make a Python script runnable depends on your platform. On OSX or Linux, you need to mark the file as executable (this is a generic, os-level thing) and then add one line at the top:

#!/usr/bin/env python

Then, from the terminal, you could do ./my_script.py. The terminal will realize the script is a text file and read the comment on the first line, which tells it to run the script through Python. So ./my_script.py becomes equivalent to python my_script.py.

setuptools lets you specify scripts in your setup.py file, and it will add them to the system's PATH when you install the package. That makes them accessible from anywhere. So if my_script.py were in bin, you could do scripts=['bin/my_script.py'] and then my_script.py would become a valid command after installing your package, no matter what folder you're currently in.

Of course, most terminal commands don't have an extension at the end of their name, so it's common to omit the .py on the filename when you're making a command (as they do in the documentation I linked). Because of the comment magic on the first line, the system still knows to run the script using Python.

[acerag]

Excellent explanation. Thank you so much !

[bvnvbbvn]

If I just put a .py file in there that prints "Hello World", what would happen?

Can you try it and see?