--- a/getting-started-strings/quickref.tex	Wed Nov 10 10:24:03 2010 +0530
+++ b/getting-started-strings/quickref.tex	Wed Nov 10 10:47:21 2010 +0530
@@ -1,8 +1,8 @@
-Creating a linear array:\\
-{\ex \lstinline|    x = linspace(0, 2*pi, 50)|}
+Creating a string:\\
+{\ex \lstinline|    s = ``Hello World''|} -- Single quotes and triple
+quotes can also be used.  
 
-Plotting two variables:\\
-{\ex \lstinline|    plot(x, sin(x))|}
+Accessing individual elements:\\
+{\ex \lstinline|   s[5]|} -- Elements can be accessed with their index
 
-Plotting two lists of equal length x, y:\\
-{\ex \lstinline|    plot(x, y)|}
+Strings are immutable. 

--- a/getting-started-strings/script.rst	Wed Nov 10 10:24:03 2010 +0530
+++ b/getting-started-strings/script.rst	Wed Nov 10 10:47:21 2010 +0530
@@ -30,9 +30,9 @@
 
 {{{ Show the slide containing the outline }}}
 
-In this tutorial, we will learn what do we actually mean by strings in
-python, how python supports the use of strings. We will also learn
-some of the operations that can be performed on strings.
+In this tutorial, we will look at what we really mean by strings, how
+python supports the use of strings and some of the operations that can
+be performed on strings. 
 
 {{{ Shift to terminal and start ipython }}}
 
@@ -42,10 +42,9 @@
 
 on the terminal
 
-So what are strings? In Python anything within either single quotes
+So, what are strings? In Python anything within either single quotes
 or double quotes or triple single quotes or triple double quotes are
-strings. This is true whatsoever, even if there is only one character
-within the quotes
+strings. 
 
 {{{ Type in ipython the following and read them as you type }}}::
 
@@ -54,19 +53,21 @@
   '''This is a string as well'''
   """This is also a string"""
   'p'
+  ""
 
-Having more than one control character to define strings come as very
-handy when one of the control characters itself is part of the
-string. For example::
+Note that it really doesn't matter how many characters are present in
+the string. The last example is a null string or an empty string. 
+
+Having more than one control character to define strings is handy when
+one of the control characters itself is part of the string. For
+example::
 
   "Python's string manipulation functions are very useful"
 
-In this case we use single quote for apostrophe. If we had only single
-quote to define strings we should have a clumsy way of escaping the
-single quote character to make it part of the string. Hence this is a
-very handy feature.
+By having multiple control characters, we avoid the need for
+escaping characters -- in this case the apostrophe. 
 
-The triple quoted strings let us define multi-lines strings without
+The triple quoted strings let us define multi-line strings without
 using any escaping. Everything within the triple quotes is a single
 string no matter how many lines it extends::
 
@@ -99,19 +100,63 @@
 gives another string in which the original string 'Hello' is repeated
 5 times.
 
-Since strings are collections we can access individual items in the
-string using the subscripts::
+Following is an exercise that you must do. 
+
+%% %% Obtain the string ``%% -------------------- %%`` (20 hyphens)
+      without typing out all the twenty hyphens. 
+
+Please, pause the video here. Do the exercise and then continue. 
+
+::
+
+  s = "%% " + "-"*20 + " %%"
+
+Let's now look at accessing individual elements of strings. Since,
+strings are collections we can access individual items in the string
+using the subscripts::
 
   a[0]
 
 gives us the first character in the string. The indexing starts from 0
-for the first character up to n-1 for the last character. We can
-access the strings from the end using negative indices::
+for the first character and goes up to n-1 for the last character. We
+can access the strings from the end using negative indices::
+
+  a[-1]
 
-  a[-2]
+gives us the last element of the string and 
+::
+
+    a[-2]
 
 gives us second element from the end of the string
 
+Following is an exercise that you must do. 
+
+%% %% Given a string, ``s = "Hello World"``, what is the output of::
+
+      s[-5] 
+      s[-10]
+      s[-15]
+
+Please, pause the video here. Do the exercise and then continue. 
+
+::
+
+  s[-5] 
+
+gives us 'W'
+::
+
+  s[-10] 
+
+gives us 'e' and 
+::
+
+  s[-15] 
+
+gives us an ``IndexError``, as should be expected, since the string
+given to us is only 11 characters long. 
+
 Let us attempt to change one of the characters in a string::
 
   a = 'hello'
@@ -132,7 +177,7 @@
 
   * How to define strings
   * Different ways of defining a string
-  * String concatenation and repeatition
+  * String concatenation and repetition
   * Accessing individual elements of the string
   * Immutability of strings
 

--- a/getting-started-strings/slides.org	Wed Nov 10 10:24:03 2010 +0530
+++ b/getting-started-strings/slides.org	Wed Nov 10 10:47:21 2010 +0530
@@ -18,7 +18,7 @@
 #+LaTeX_HEADER:  commentstyle=\color{red}\itshape, stringstyle=\color{darkgreen},
 #+LaTeX_HEADER:  showstringspaces=false, keywordstyle=\color{blue}\bfseries}
 
-#+TITLE:    Accessing parts of arrays
+#+TITLE:    
 #+AUTHOR:    FOSSEE
 #+EMAIL:     
 #+DATE:    
@@ -30,81 +30,38 @@
 #+OPTIONS:   TeX:t LaTeX:nil skip:nil d:nil todo:nil pri:nil tags:not-in-toc
 
 * Outline
-  - Manipulating one and multi dimensional arrays
-  - Access and change individual elements 
-  - Access and change rows and columns 
-  - Slicing and striding on arrays to access chunks 
-  - Read images into arrays and manipulations
-* Sample Arrays
-  #+begin_src python
-    In []: A = array([12, 23, 34, 45, 56])
-    
-    In []: C = array([[11, 12, 13, 14, 15],
-                      [21, 22, 23, 24, 25],
-                      [31, 32, 33, 34, 35],
-                      [41, 42, 43, 44, 45],
-                      [51, 52, 53, 54, 55]])
-    
-  #+end_src
+*** Defining strings
+*** Concatenation
+*** Accessing individual elements
+*** Immutability of strings
 * Question 1
-  Change the last column of ~C~ to zeroes. 
+  Obtain the string ~%% -------------------- %%~ (20 hyphens) without
+  typing out all the twenty hyphens.
 * Solution 1
   #+begin_src python
-    In []:  C[:, -1] = 0
+    s = "%% " + "-"*20 + " %%"
   #+end_src
 * Question 2
-  Change ~A~ to ~[11, 12, 13, 14, 15]~. 
+  Given a string, ~s~ which is ~Hello World~ , what is the output of::
+  #+begin_src python
+    s[-5] 
+    s[-10]
+    s[-15]
+  #+end_src
 * Solution 2
   #+begin_src python
-    In []:  A[:] = [11, 12, 13, 14, 15]
-  #+end_src
-* squares.png
-  #+begin_latex
-    \begin{center}
-      \includegraphics[scale=0.6]{squares}    
-    \end{center}
-  #+end_latex
-* Question 3
-  - obtain ~[22, 23]~ from ~C~. 
-  - obtain ~[11, 21, 31, 41]~ from ~C~. 
-  - obtain ~[21, 31, 41, 0]~.   
-* Solution 3
-  #+begin_src python
-    In []:  C[1, 1:3]
-    In []:  C[0:4, 0]
-    In []:  C[1:5, 0]
-  #+end_src
-* Question 4
-  Obtain ~[[23, 24], [33, -34]]~ from ~C~
-* Solution 4
-  #+begin_src python
-    In []:  C[1:3, 2:4]
-  #+end_src
-* Question 5
-  Obtain the square in the center of the image
-* Solution 5
-  #+begin_src python
-    In []: imshow(I[75:225, 75:225])
-  #+end_src
-* Question 6
-  Obtain the following
-  #+begin_src python
-    [[12, 0], [42, 0]]
-    [[12, 13, 14], [0, 0, 0]]
-  #+end_src
-
-* Solution 6
-  #+begin_src python
-    In []: C[::3, 1::3]
-    In []: C[::4, 1:4]
+    'W'
+    'e'
+    IndexError
   #+end_src
 * Summary
-  You should now be able to --
-  - Manipulate 1D \& Multi dimensional arrays
-      - Access and change individual elements 
-      - Access and change rows and columns 
-      - Slice and stride on arrays
-  - Read images into arrays and manipulate them.
+  In this tutorial we have learnt
+    + How to define strings
+    + Different ways of defining a string
+    + String concatenation and repetition
+    + Accessing individual elements of the string
+    + Immutability of strings
+  
 * Thank you!
 #+begin_latex
   \begin{block}{}

--- a/getting-started-strings/slides.tex	Wed Nov 10 10:24:03 2010 +0530
+++ b/getting-started-strings/slides.tex	Wed Nov 10 10:47:21 2010 +0530
@@ -1,95 +1,118 @@
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-%Tutorial slides on Python.
-%
-% Author: FOSSEE 
-% Copyright (c) 2009, FOSSEE, IIT Bombay
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-
-\documentclass[14pt,compress]{beamer}
-%\documentclass[draft]{beamer}
-%\documentclass[compress,handout]{beamer}
-%\usepackage{pgfpages} 
-%\pgfpagesuselayout{2 on 1}[a4paper,border shrink=5mm]
-
-% Modified from: generic-ornate-15min-45min.de.tex
-\mode<presentation>
-{
-  \usetheme{Warsaw}
-  \useoutertheme{infolines}
-  \setbeamercovered{transparent}
-}
-
-\usepackage[english]{babel}
+% Created 2010-11-10 Wed 10:46
+\documentclass[presentation]{beamer}
 \usepackage[latin1]{inputenc}
-%\usepackage{times}
 \usepackage[T1]{fontenc}
-
-\usepackage{ae,aecompl}
-\usepackage{mathpazo,courier,euler}
-\usepackage[scaled=.95]{helvet}
+\usepackage{fixltx2e}
+\usepackage{graphicx}
+\usepackage{longtable}
+\usepackage{float}
+\usepackage{wrapfig}
+\usepackage{soul}
+\usepackage{textcomp}
+\usepackage{marvosym}
+\usepackage{wasysym}
+\usepackage{latexsym}
+\usepackage{amssymb}
+\usepackage{hyperref}
+\tolerance=1000
+\usepackage[english]{babel} \usepackage{ae,aecompl}
+\usepackage{mathpazo,courier,euler} \usepackage[scaled=.95]{helvet}
+\usepackage{listings}
+\lstset{language=Python, basicstyle=\ttfamily\bfseries,
+commentstyle=\color{red}\itshape, stringstyle=\color{darkgreen},
+showstringspaces=false, keywordstyle=\color{blue}\bfseries}
+\providecommand{\alert}[1]{\textbf{#1}}
 
-\definecolor{darkgreen}{rgb}{0,0.5,0}
-
-\usepackage{listings}
-\lstset{language=Python,
-    basicstyle=\ttfamily\bfseries,
-    commentstyle=\color{red}\itshape,
-  stringstyle=\color{darkgreen},
-  showstringspaces=false,
-  keywordstyle=\color{blue}\bfseries}
-
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-% Macros
-\setbeamercolor{emphbar}{bg=blue!20, fg=black}
-\newcommand{\emphbar}[1]
-{\begin{beamercolorbox}[rounded=true]{emphbar} 
-      {#1}
- \end{beamercolorbox}
-}
-\newcounter{time}
-\setcounter{time}{0}
-\newcommand{\inctime}[1]{\addtocounter{time}{#1}{\tiny \thetime\ m}}
-
-\newcommand{\typ}[1]{\lstinline{#1}}
-
-\newcommand{\kwrd}[1]{ \texttt{\textbf{\color{blue}{#1}}}  }
-
-% Title page
-\title{Your Title Here}
-
-\author[FOSSEE] {FOSSEE}
-
-\institute[IIT Bombay] {Department of Aerospace Engineering\\IIT Bombay}
+\title{}
+\author{FOSSEE}
 \date{}
 
-% DOCUMENT STARTS
+\usetheme{Warsaw}\usecolortheme{default}\useoutertheme{infolines}\setbeamercovered{transparent}
 \begin{document}
 
+
+
+
+
+
+
+
+
+
+
 \begin{frame}
-  \maketitle
+\frametitle{Outline}
+\label{sec-1}
+\begin{itemize}
+
+\item Defining strings\\
+\label{sec-1_1}%
+\item Concatenation\\
+\label{sec-1_2}%
+\item Accessing individual elements\\
+\label{sec-1_3}%
+\item Immutability of strings\\
+\label{sec-1_4}%
+\end{itemize} % ends low level
 \end{frame}
+\begin{frame}
+\frametitle{Question 1}
+\label{sec-2}
 
+  Obtain the string \texttt{\%\% -------------------- \%\%} (20 hyphens) without
+  typing out all the twenty hyphens.
+\end{frame}
 \begin{frame}[fragile]
-  \frametitle{Outline}
-  \begin{itemize}
-    \item 
-  \end{itemize}
+\frametitle{Solution 1}
+\label{sec-3}
+
+\lstset{language=Python}
+\begin{lstlisting}
+s = "%% " + "-"*20 + " %%"
+\end{lstlisting}
 \end{frame}
+\begin{frame}[fragile]
+\frametitle{Question 2}
+\label{sec-4}
 
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-%%              All other slides here.                  %%
-%% The same slides will be used in a classroom setting. %% 
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-
+  Given a string, \texttt{s} which is \texttt{Hello World} , what is the output of::
+\lstset{language=Python}
+\begin{lstlisting}
+s[-5] 
+s[-10]
+s[-15]
+\end{lstlisting}
+\end{frame}
 \begin{frame}[fragile]
-  \frametitle{Summary}
-  \begin{itemize}
-    \item 
-  \end{itemize}
+\frametitle{Solution 2}
+\label{sec-5}
+
+\lstset{language=Python}
+\begin{lstlisting}
+'W'
+'e'
+IndexError
+\end{lstlisting}
 \end{frame}
-
 \begin{frame}
-  \frametitle{Thank you!}  
+\frametitle{Summary}
+\label{sec-6}
+
+  In this tutorial we have learnt
+\begin{itemize}
+\item How to define strings
+\item Different ways of defining a string
+\item String concatenation and repetition
+\item Accessing individual elements of the string
+\item Immutability of strings
+\end{itemize}
+
+  
+\end{frame}
+\begin{frame}
+\frametitle{Thank you!}
+\label{sec-7}
+
   \begin{block}{}
   \begin{center}
   This spoken tutorial has been produced by the

--- a/progress.org	Wed Nov 10 10:24:03 2010 +0530
+++ b/progress.org	Wed Nov 10 10:47:21 2010 +0530
@@ -15,7 +15,7 @@
 |---------+----------------------------------------+-------+----------+-----------------+-----------|
 | 3.1 LO: | getting started with lists             |     2 | Amit     | Anoop(Done)     |           |
 | 3.2 LO: | getting started with =for=             |     2 | Anoop    | Nishanth (Done) |           |
-| 3.3 LO: | getting started with strings           |     2 | Madhu    | Punch (Pending) |           |
+| 3.3 LO: | getting started with strings           |     2 | Madhu    | Punch (Done)    |           |
 | 3.4 LO: | getting started with files             |     3 | Punch    | Anoop(Done)     |           |
 | 3.5 LO: | parsing data                           |     3 | Nishanth | Amit (Done)     |           |
 | 3.6 LO: | statistics                             |     2 | Amit     | Punch (Done)    |           |