What is setup.py?

Question

Can anyone please explain what setup.py is and how it can be configured or used?

Answer 1

It helps to install a python package foo on your machine (can also be in virtualenv) so that you can import the package foo from other projects and also from [I]Python prompts.

It does the similar job of pip, easy_install etc.,

---

Using setup.py

Let's start with some definitions:

Package - A folder/directory that contains __init__.py file.
Module - A valid python file with .py extension.
Distribution - How one package relates to other packages and modules.

Let's say you want to install a package named foo. Then you do,

$ git clone https://github.com/user/foo  
$ cd foo
$ python setup.py install

Instead, if you don't want to actually install it but still would like to use it. Then do,

$ python setup.py develop  

This command will create symlinks to the source directory within site-packages instead of copying things. Because of this, it is quite fast (particularly for large packages).

---

Creating setup.py

If you have your package tree like,

foo
├── foo
│   ├── data_struct.py
│   ├── __init__.py
│   └── internals.py
├── README
├── requirements.txt
└── setup.py

Then, you do the following in your setup.py script so that it can be installed on some machine:

from setuptools import setup

setup(
   name='foo',
   version='1.0',
   description='A useful module',
   author='Man Foo',
   author_email='foomail@foo.com',
   packages=['foo'],  #same as name
   install_requires=['bar', 'greek'], #external packages as dependencies
)

Instead, if your package tree is more complex like the one below:

foo
├── foo
│   ├── data_struct.py
│   ├── __init__.py
│   └── internals.py
├── README
├── requirements.txt
├── scripts
│   ├── cool
│   └── skype
└── setup.py

Then, your setup.py in this case would be like:

from setuptools import setup

setup(
   name='foo',
   version='1.0',
   description='A useful module',
   author='Man Foo',
   author_email='foomail@foo.com',
   packages=['foo'],  #same as name
   install_requires=['bar', 'greek'], #external packages as dependencies
   scripts=[
            'scripts/cool',
            'scripts/skype',
           ]
)

---

Add more stuff to (setup.py) & make it decent:

from setuptools import setup

with open("README", 'r') as f:
    long_description = f.read()

setup(
   name='foo',
   version='1.0',
   description='A useful module',
   license="MIT",
   long_description=long_description,
   author='Man Foo',
   author_email='foomail@foo.com',
   url="http://www.foopackage.com/",
   packages=['foo'],  #same as name
   install_requires=['bar', 'greek'], #external packages as dependencies
   scripts=[
            'scripts/cool',
            'scripts/skype',
           ]
)

The long_description is used in pypi.org as the README description of your package.

---

And finally, you're now ready to upload your package to PyPi.org so that others can install your package using pip install yourpackage.

First step is to claim your package name & space in pypi using:

$ python setup.py register

Once your package name is registered, nobody can claim or use it. After successful registration, you have to upload your package there (to the cloud) by,

$ python setup.py upload

Optionally, you can also sign your package with GPG by,

$ python setup.py --sign upload

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Bonus: See a sample setup.py from a real project here: torchvision-setup.py