brip 0.3.0

brip stands for Brython's pip. It brings the Python Package Index (PyPI) ecosystem and the pip-like workflow to Brython-powered project.

brip - The Brython Package Installer

brip stands for Brython's pip. It brings the Python packages ecosystem and the pip-like workflow to Brython-powered projects.

You can use brip to install packages from the PyPI and other indexes, into your different Brython project.

Problem Statement

• Historically, most brython-oriented Python packages are pre-compiled into - and distributed as - a javascript file. This works well for those self-contained Python packages, but when/if a Python package has its own dependencies, there was no obvious way to declare and manage those dependencies.
• In general, there was no Pythonic way to install a generic Python package and their dependencies, directly from PyPI into your Brython project.

brip is developed to bring the PyPI ecosystem and the familiar pip-like workflow to Brython-powered projects.

Quickstart: A complete sample project

There is a complete sample project, Easter, to demonstrate how to use brip.

Installation

Just run pip install brip.

It is recommended that you install brip into one central virtual environment, rather than installing brip inside each of your brython project's environment. (In fact, your Brython project technically does not need its own virtual environment.)

Installation on Linux and macOS:

python3 -m venv ~/venv_central
source ~/venv_central/bin/activate
pip install brip

Installation on Windows:

py -m venv $HOME\venv_central
$HOME\venv_central\Scripts\activate.bat
pip install brip

Manual: Command-line usage

This manual assumes you use Linux or macOS. Windows users please adjust the path separator in each sample.

• Install a package from PyPI into your Brython project's web root directory (i.e. the directory containing your index.html):

  cd my_brython_project_one/website
  brip install SomePackage
  

  Now a new site-packages.brython.js is generated in current directory, containing SomePackage and its dependencies. Your Brython project's index.html would just need to add a line <script src="site-packages.brython.js"></script>, from now on you can use import some_package inside your Brython project!

  Package installed by brip is obtained directly from PyPI. You do NOT need to install the package by pip first.

• List what packages are installed for current Brython project (or more precisely speaking, list packages contained in site-packages.brython.js):

  cd my_brython_project_one/website
  brip list
  

  Note: Packages installed by brip are not visible to pip list, and vice versa. Because their installation target are completely different.

• Install several packages from PyPI into your Brython project's web root directory (i.e. the directory containing your index.html):

  cd my_brython_project_two/website
  brip install -r brequirements.txt
  

  The file "brequirements.txt" has a format identical to pip's "requirements.txt", and it can be named whatever name you want. We recommend using a name different than pip's conventional "requirements.txt", though, such as "brequirements.txt", to remind you that its content are meant to be installed by brip, not by pip.

• Uninstalling a package ... is not directly supported, but can be achieved by organizing your full dependency list in a "brequirements.txt" file, and then use this pattern:

  cd my_brython_project_two/website
  
  # Use your editor to remove one package name
  edit brequirements.txt
  
  # Each install will OVERWRITE existing site-packages.brython.js
  brip install -r brequirements.txt
  

Differences to pip

In pip you can do incremental installation. If you run pip install foo and then pip install bar, you would end up with both foo and bar installed.

But, due to some technical reason, brip always do overwrite installation. If you run brip install foo and then brip install bar, you would end up with only bar available in your Brython project.

Therefore, we recommend you always use a "brequirements.txt" to organize your project's full dependency. That way, any adjustment to such a file would be flushed to your Brython project by next brip install -r brequirements.txt.

brip also only implements a small subset of pip. Please refer to the command-line help brip -h or brip install -h etc..

Limitations

brip aims to bring the entire Python Package Index (PyPI) ecosystem to Brython. However, in reality there are some limitations outside of the control of brip.

• Brython-powered applications are running inside a browser. The browser is a capable virtual machine in its own right. However, many Python packages are not expected to be run inside a browser. For example, file system behaves differently in Brython: Writing is impossible, and reading is limited to the folders accessible with an Ajax request.

• Brython itself only supports pure Python packages. That excludes packages which are partially written in C, such as numpy. Consequently, only those packages written in pure Python and its entire dependency chain written in pure Python, would work in Brython.

• As of this writing, Brython 3.10.5 does not support converting namespace packages into a loadable javascript file.

• Sometimes, even pure Python package might not work in Brython, due to some subtle differences between Brython and CPython.

• Unfortunately, there is currently no straightforward way to know whether a Python package would work in Brython. You probably have to rely on trial-and-error. Just use brip to install a package, use it in Brython environment, and see if the browser console logs any error.

Feel free to report those packages into brip's issue list. brip might not be in position to solve it directly, but the community might be able to help.

Recipe for Brython-friendly package's maintainers

While we mentioned in the Problem Statement that brip was mainly developed to allow Brython app developers to pull generic Python packages from PyPI, for example:

# Inside the brequirements.txt, it contains the following line
charts.css.py>=0.4,<1

there is nothing wrong for a self-contained, Brython-friendly package to be distributed as a javascript file, for example:

<!-- Inside the index.html, it contains the following line -->
<script src='https://github.com/rayluo/charts.css.py/releases/download/0.4.0/charts.css.py-brython.js'></script>

Here, the term "Brython-friendly" is defined as a generic, pure Python package that can be released to PyPI, but it is also designed to be able to work in Brython.

So, how do you - a Brython-friendly package's maintainer - generate that javascript file?

Here is how I pack my package charts.css.py into a charts.css.py-brython.js:

cd charts.css.py
brip install .
# Now a site-packages.brython.js is generated in current directory,
# containing the PyPI-ready project in current directory.
# I just need to rename it to charts.css.py-brython.js and distribute it.

While doing so, you may see a warning message on your console:

  DEPRECATION: A future pip version will change local packages to be built in-place without first copying to a temporary directory. We recommend you use --use-feature=in-tree-build to test your packages with this new behavior before it becomes the default.
   pip 21.3 will remove support for this functionality. You can find discussion regarding this at https://github.com/pypa/pip/issues/7555.

You can just ignore that message. It has no negative impact to your javascript outcome.

That warning message is expected to be gone once pip 21.3 becomes available and you upgrade to it (by running python -m pip install --upgrade pip).