Easter Distribution

This project shows how Easters within a century are distributed among months and dates,
and how Easter date swings back and forth, year after year.
It is in action here.

This project is also designed to be a sample of how to use
brip
to pull in generic pure Python packages into your
Brython-powered project.

How to develop a project like this?

We chose to implement the following features in this sample project,
to showcase how generic Python packages could be pulled into your project by brip.

Calculate the Easter date of any given year.
Easter calculation is complicated,
but it is made easy by this generic Python package
python-dateutil.
Show the distribution of Easters in charts,
with the help of this generic Python package
charts.css.py.

So, how to build a Brython project to utilize the above 2 generic Python packages?

Prerequisite:
You do NOT need to install those 2 packages by the normal pip.
Instead, you use pip to install brip into a virtual environment,
once and for all:
such an environment can be shared among all your Brython projects.

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
```
Create an empty Brython project.
You can start from scratch, or clone or download this
template Brython project.
Inside your Brython project’s webroot directory
(i.e. the directory containing your index.html),
create a brequirements.txt file containing your dependencies.
After you finish that, your project structure could be something like this.
```
 easter
 ├── website
 │   ├── index.html
 │   ├── ...
 │   └── brequirements.txt
 └── README.md
```
Your brequirements.txt declares dependencies, optionally with their version ranges.
```
python-dateutil<3
charts.css.py>=0.4.0,<1
```
For what it’s worth, the python-dateutil package has its own dependency on six,
but you don’t have to know, brip will automatically pull in all dependencies for you.
Run brip install -r brequirements.txt.
This will generate a site-packages.brython.js file,
which contains the packages that you declared, as well as all their dependencies.
In your Brython project’s index.html, include the brython.js as usual,
and you would typically also need to include the brython_stdlib.js,
lastly you include the site-packages.brython.js that we generated just now.

That is all.
Now you can use import dateutil and import charts.css in your Brython project.
Once you finish your project, you can deploy it with the generated
site-packages.brython.js.

Alternatively, this project chooses to
run step 4 on-the-fly via Github Actions,
and then deploy the website to Github Pages
(with the help from another tool named Github Page Overwriter).
The end result is you do not even need to hardcode a copy of site-packages.brython.js
inside your project’s code base.
See how clean our code base is.

Caveat

The two external dependencies, python-dateutil and charts.css.py,
work smooth inside Brython.
But the reality is, not every PyPI packages would work fine.
Please refer to the limitations of brip
for more details.