new indexing figures for python

programming/python_lecture_en/programming.tex

@@ -2,8 +2,20 @@
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
 \chapter{Programming in Python}
 
+Python is a rather young and very dynamic programming languages which
+attracts more and more users in the sciences. One of the reasons is
+that python is an expressive language, that means, the program code
+can often be literally read and understood. Another aspect is the
+strong community support. Most packages are developed by open-source
+enthusiasts who are willing to share their code and knowledge thus,
+answers to most problems can be found with a simple internet search.
+
 \section{Variables and Datatypes}
 
+Befor we can start to solve programming problems we have to know a few
+basic things about the programming language. In this chapter the
+basic concepts and the python syntax will be introduced.  
+
 \subsection{Variables}
 
 A \enterm{variable} is basically a pointer to a place in a computer's
@@ -18,7 +30,6 @@ same bitpattern is stored but the interpretation as an 8-bit
 \enterm{integer} leads to the numeric value of 38 while an
 interpretation as a \enterm{character} lead to the ampersand symbol. 
 
-
 \begin{figure}
   \centering
   \begin{subfigure}{.5\textwidth}
@@ -43,11 +54,13 @@ Variables can be created at any time at any place in a python
 program. Listing \ref{varListing1} shows different ways to do this:
 
 \begin{lstlisting}[label=varListing1, caption={Creating variables.}, language=python]
+w = 3.1415
 x = 38
-y = None
+y = 'A'
-z = 'A'
+z = None
 \end{lstlisting}
 
+Line one creates 
 Die Zeile 1 kann etwa so gelesen werden:''Erzeuge eine Variable mit
 dem Namen \varcode{x} und weise ihr den Wert 38 zu''.  Das
 Gleichheitszeichen ist der sogenannte
@@ -299,7 +312,7 @@ ans =
 
 \subsubsection{Zugriff auf Inhalte von Vektoren}
 \begin{figure}
-  \includegraphics[width=0.4\columnwidth]{arrayIndexing}
+  \includegraphics[width=0.4\columnwidth]{arrayIndexing_py}
   \titlecaption{Indices von Vektoren.}{Jedes Feld eines Vektors hat
     einen Index (kleine Zahl) mit dem auf den jeweiligen Inhalt
     (gro{\ss}e Zahl) zugegriffen werden
@@ -593,7 +606,7 @@ die Gr\"o{\ss}e der l\"angsten Dimension aus. Die \code{size()}-Funktion
 gibt dagegen die L\"ange jeder Dimension als Vektor zur\"uck.
 
 \begin{figure}
-  \includegraphics[width=0.9\columnwidth]{matrixIndexing}
+  \includegraphics[width=0.9\columnwidth]{matrixIndexing_py}
   \titlecaption{Indices von Matrizen.}{Jedes Feld einer Matrize
     wird durch einen Index individuell angesprochen. Der Index setzt
     sich aus so vielen Zahlen zusammen wie es Dimensionen gibt (links