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Python for Beginners

What is Python?

The Language:
- A modern, robust, high level programming language created by Guido van Rossum.
- First appeared in 20 February 1991.
- Official website: http://www.python.org
- Two incompatible versions:
  - Python 3
  - Python 2 <--- will die in 2020!

The Implementation:
- CPython (the standard, written in C) <--- you'll probably use this one.
- Pypy (written in RPython) <--- ~7.5x faster than CPython! Still immature for general usage.
- Jython (for Java platform)
- IronPython (for .NET Framework)
- ...

Basic Setup

Python should come pre-installed by default on most Linux distros.
However it might not be the version you want to (or should) use.

Should I use Python 2 or Python 3?
- If you are a new user, go for Python 3!
- If you are using Python 2 already, please try to upgrade your scripts to Python 3.
- In this tutorial I'll focus on Python 3.

Check which version of Python you have installed on your system:
```
python --version
  Python 3.6.0
```
Great, I have Python 3! If you see something like:
```
python --version
  Python 2.7.13
```
it means that python points to Python 2. In such case, try this:
```
python3 --version
  Python 3.6.0
```
If the last command returns an error, then please install Python 3:
```
sudo apt-get install python3
```

From now on make sure you always run your scripts with Python 3 by typing:
```
python3 myscript.py
```
instead of (maybe Python 2 or 3):
```
python myscript.py
```

IPython & Jupyter notebook

Make sure you install a version compatible with Python 3:

sudo apt-get install ipython3 jupyter

Note: if your system's repository doesn't provide the jupyter package yet, try to install the ipython3-notebook package instead.

`ipython`

A powerful interactive Python shell.

To launch an ipython session from a terminal:
```
ipython
```
ipython is great for doing some experimentation or discover something new about the language.
To exit the session just press Ctrl-D or close the terminal.
Note: After exit your entire session will be lost!

`jupyter notebook`

Jupyter is the evolution of ipython ...eh, like a Pokemon! :-p

To launch a jupyter notebook (or ipython notebook) server from a terminal:
```
ipython notebook
```
or
```
jupyter notebook
```
It'll run on a webbrowser. We are using jupyter right now! :-)
We can save our work and keep it organized on individual notebooks!

Installing Additional Modules/Packages

Always prefer to install things from your system's repository!

Let's install a few usefull packages:

sudo apt-get install python3-numpy python3-scipy python3-matplotlib

What if a package I need is not in the repository?

If you have no choice, then first you have to install pip:
```
sudo apt-get install python3-pip
```
and use pip to install additional modules.

Note: When installing things with pip, never use sudo! I mean, don't do this:

~~sudo pip install modulename~~

or you might risk breaking your system!!!

Instead, you should pip-install modules locally, which is safe and you won't mess with your system.

For example:
```
pip3 install --user modulename
```
will install the modulename package under ~/.local/lib/python3.X/site-packages

To uninstall it:
```
pip3 uninstall modulename
```

Additional Resources

Official Documentation: https://docs.python.org/3/
The Python Tutorial: https://docs.python.org/3/tutorial/index.html
The Standard Python Library: https://docs.python.org/3/py-modindex.html
What's New in Python: https://docs.python.org/3/whatsnew/index.html
Python Enhancement Proposals (PEPs): https://www.python.org/dev/peps/
Python Package Index (PYPI): https://pypi.python.org/pypi

Awesome Python: https://awesome-python.com/
The Hitchhiker’s Guide to Python!: http://docs.python-guide.org/en/latest/
From Python to Numpy: http://www.labri.fr/perso/nrougier/from-python-to-numpy/
Scipy Lecture Notes http://www.scipy-lectures.org/