# Python¶

## What is Python?¶

From www.python.org:

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). 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 comp.lang.python – or just try compiling Python yourself.

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

The place to start is www.python.org where you will find plenty of information on Python including tutorials.

## What do I need to import in order to use PyX?¶

It is recommended to begin your Python code with:

from pyx import *


when using PyX. This allows you for example to write simply graph.graphxy instead of pyx.graph.graphxy. The following modules will be loaded: attr, box, bitmap, canvas, color, connector, deco, deformer, document, epsfile, graph, path, pattern, style, trafo, text, and unit.

For convenience, you might import specific objects of a module like in:

from graph import graphxy


which allows you to write graphxy() instead of graph.graphxy().

All code segments in this document assume that the import line mentioned in the first code snippet is present.

## What is a raw string and why should I know about it when using PyX?¶

The backslash serves in standard Python strings to start an escape sequence. For example \n corresponds to a newline character. On the other hand, TeX and LaTeX, which do the typesetting in PyX, use the backslash to indicate the start of a command. In order to avoid the standard interpretation, the string should be marked as a raw string by prepending it by an r like in:

c.text(0, 0, r"$\alpha\beta\gamma$")