Dive Into Python is a Python book for experienced programmers. You can buy a printed copy, read it online, or download it in a variety of formats. It is also available in multiple languages.

http://diveintopython.org/toc/index.htm

What is Python?
Python is an interpreted, interactive, object-oriented programming language. It is often compared to Tcl, Perl, Scheme or Java.

Python combines remarkable power with very clear syntax. It has modules, classes, exceptions, very high level dynamic data types, and dynamic typing. There are interfaces to many system calls and libraries, as well as to various windowing systems (X11, Motif, Tk, Mac, MFC, wxWidgets). New built-in modules are easily written in C or C++. Python is also usable as an extension language for applications that need a programmable interface.

The Python implementation is portable: it runs on many brands of UNIX, on Windows, OS/2, Mac, Amiga, and many other platforms. If your favorite system isn’t listed here, it may still be supported, if there’s a C compiler for it. Ask around on news:comp.lang.python — or just try compiling Python yourself.

The Python implementation is copyrighted but freely usable and distributable, even for commercial use.

Cheers,
pavs