Once you finished your installation of Python on your Windows OS,  GNU/Linux or Mac OS, let me tell you how to install it on your favorite IDE, Eclipse.

First of all, you have to download Eclipse on the official website. I suggest you to choose the JavaScript version.

Let's go.
Open Eclipse then:

Help > Eclipse Marketplace.
On the Find input, type PyDev and click the search icon.

PyDev - Python IDE for Eclipse appears.
Click the Install button on the right.

Let the all selected and click Next.
Accept the licence agreements and click Finish.
A new window asks you if you want to install an unsigned content.
You say OK and a new one appears.
Select the Aptana Pydev; Pydev; Aptana option and click OK.

Eclipse wants to restart now, so click Restart Now.

You are now able to read the file with the .py extension.
But you can not launch the python.exe yet.

So let's do it.
Click:

Window > Preferences > PyDev > Interpreter - Python > New.
Type the name you want and the Interpreter executable path, for example:

On Windows:

C:\soft\python\python3\python.exe

On GNU/Linux or Mac OS:

/usr/bin/python2.7

Click OK and let all subdirectories in yours selected, something like that:

C:\soft\python\python3\DLLs

C:\soft\python\python3\lib

C:\soft\python\python3

C:\soft\python\python3\lib\site-packages

Click OK again, you just added the Python's libraries.

To finish click Apply and OK.

To test this installation, let's create a new Python project:

Right click on the Navigator area and add a Project name: test

Select 2.7 or 3.0 in the Grammar Version area.

Click Finish.
In the src folder created, add a new file name hello.py.

Type it inside:

print('Hello World')

Save it.
There is a green icon with a white triangle in the toolbar, click it.
Choose Python Run on the window and OK.

In the Console window, you are seeing:

Hello World

Great job!
It was an important step in the Python world, you are now able to create great applications.