Jython
Another version of Python is called Jython.
"J" is for "Java". Imagine a Python written in Java instead of C. This is useful, for example, if you develop large and complex systems written entirely in Java and want to add some Python flexibility to them. The traditional CPython may be difficult to integrate into such an environment, as C and Java live in completely different worlds and don't share many common ideas.
Jython can communicate with existing Java infrastructure more effectively. This is why some projects find it useful and necessary.
Note: the current Jython implementation follows Python 2 standards. there is no Jython conforming to Python 3, so far.
PyPY and RPython
take a look at the logo below. it's rebus. Can you solve it?
It's the logo of the PyPy a Python within a Python. In other words, it represents a Python environment written in Python-like language named RPython (Restricted Python). It is a actually a subset of Python.
The source code of PyPY is not run in the interpretation manner, but is instead translated into the C programming language and then executed separately.
This is useful because if you want to test any new feature that may be (but doesn't have to be) introduced into mainstream Python implementations, it's easier to check it with PyPy than with CPython. This is why PyPy is rather a tool for people developing Python than for the rest of the users.
This doesn't make PyPy any less important or less serious than CPython, of course.
In addition, PyPy is compatible with the Python 3 language.
There are many more different Pythons int he world. You'll find them if you look, but this course will focus on CPython.
How to get Python and how to get to use it
There are several ways to get your own copy of Python 3, depending on the operating system you use.
Linux users most probably have Python already installed - this is the most likely scenario, as Python's infrastructure is intensively used by many Linux OS components.
For example, some distributors may couple their specific tools together with the system and many of these tools, like package managers, are often written in Python. Some parts of graphical environments available in the Linux world may use Python, too.
If you're a Linux user, open the terminal/console, and type:
python3
at the shell prompt, press Enter and wait.
If you see something like this:
Python 3.4.5 (default, Jan 12 2017, 02:28:40)
[GCC 4.2.1 Compatible Clang 3.7.1 (tags/RELEASE_371/final)] on linux
Type "help", "copyright", "credits" or "license" for more information.
then you don't have to do anything else.
If Python 3 is absent, then refer to your Linux documentation in order to find out how to use your package manager to download and install a new package - the one you need is named python3 or it's name begins with that.
All non-Linux users can download a copy at https://www.python.org/downloads/.
