path: root/day2/session1.tex

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%Tutorial slides on Python.
%
% Author: FOSSEE 
% Copyright (c) 2009, FOSSEE, IIT Bombay
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% Title page
\title[Basic Python]{Python language: Basics}

\author[FOSSEE Team] {The FOSSEE Group}

\institute[IIT Bombay] {Department of Aerospace Engineering\\IIT Bombay}
\date[] {SciPy.in 2010, Tutorials}
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%% Delete this, if you do not want the table of contents to pop up at
%% the beginning of each subsection:
\AtBeginSubsection[]
{
  \begin{frame}<beamer>
    \frametitle{Outline}
    \tableofcontents[currentsection,currentsubsection]
  \end{frame}
}

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    \frametitle{Outline}
    \tableofcontents[currentsection,currentsubsection]
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% DOCUMENT STARTS
\begin{document}

\begin{frame}
  \titlepage
\end{frame}

\begin{frame}
  \frametitle{Outline}
  \tableofcontents
  % You might wish to add the option [pausesections]
\end{frame}

\section{Data types}

\begin{frame}
  \frametitle{Primitive Data types}
  \begin{itemize}
    \item Numbers: float, int, complex
    \item Strings
    \item Booleans
  \end{itemize}
\end{frame}

\subsection{Numbers}
\begin{frame}[fragile]
  \frametitle{Numbers}
  \begin{itemize}
    \item \kwrd{int}\\ whole number, no matter what the size!
  \begin{lstlisting}
In []: a = 13

In []: b = 99999999999999999999
  \end{lstlisting}
    \item \kwrd{float}
  \begin{lstlisting}
In []: p = 3.141592
  \end{lstlisting}
    \item \kwrd{complex}
  \begin{lstlisting}
In []: c = 3+4j
  \end{lstlisting}
  \end{itemize}
\end{frame}

\subsection{Booleans}
\begin{frame}[fragile]
  \frametitle{Booleans}
  \begin{lstlisting}
In []: t = True

In []: F = not t

In []: F or t
Out[]: True

In []: F and t
Out[]: False
  \end{lstlisting}
%%  \inctime{5}
\end{frame}

\begin{frame}[fragile]
  \frametitle{( )  for precedence}
  \begin{lstlisting}
In []: a = False
In []: b = True
In []: c = True

In []: (a and b) or c
Out[]: True

In []: a and (b or c)
Out[]: False
  \end{lstlisting}
%%  \inctime{5}
\end{frame}

\subsection{Strings}

\begin{frame}[fragile]
\frametitle{Strings}
Anything within ``quotes'' is a string!
\begin{lstlisting}
' This is a string '  
" This too! "
""" This one too! """
''' And one more! '''
\end{lstlisting}
\end{frame}

\begin{frame}[fragile]
\frametitle{Strings}
Why so many?
\begin{lstlisting}
' "Do or do not.  No try." said Yoda.'  
" ' is a mighty lonely quote."
\end{lstlisting}
The triple quoted ones can span multiple lines!

\begin{lstlisting}
""" The quick brown
fox jumped over
    the lazy dingbat. 
"""
\end{lstlisting}
\end{frame}

\begin{frame}[fragile]
  \frametitle{Strings}
  \begin{lstlisting}
In []: w = "hello"

In []: print w[0], w[1], w[-1]

In []: len(w)
Out[]: 5
  \end{lstlisting}
\end{frame}

\begin{frame}[fragile]
  \frametitle{Strings \ldots}
  \emphbar{Strings are immutable}
  \begin{lstlisting}
In []: w[0] = 'H' 
  \end{lstlisting}
  \pause
  \begin{lstlisting}
--------------------------------------------
TypeError  Traceback (most recent call last)

<ipython console> in <module>()

TypeError: 'str' object does not
         support item assignment
  \end{lstlisting}
\end{frame}

\section{Operators}

\begin{frame}[fragile]
  \frametitle{Arithmetic operators}
  \small
  \begin{lstlisting}
In []: 1786 % 12
Out[]: 10

In []: 45 % 2
Out[]: 1

In []: 864675 % 10
Out[]: 5

In []: 3124 * 126789
Out[]: 396088836

In []: big = 1234567891234567890 ** 3

In []: verybig = big * big * big * big
  \end{lstlisting}
\end{frame}

\begin{frame}[fragile]
  \frametitle{Arithmetic operators}
  \begin{lstlisting}
In []: 17 / 2
Out[]: 8

In []: 17 / 2.0
Out[]: 8.5

In []: 17.0 / 2
Out[]: 8.5

In []: 17.0 / 8.5
Out[]: 2.0
  \end{lstlisting}
\end{frame}

\begin{frame}[fragile]
\frametitle{Arithmetic operators}
  \begin{lstlisting}
In []: c = 3+4j

In []: abs(c)
Out[]: 5.0

In []: c.imag
Out[]: 4.0

In []: c.real
Out[]: 3.0
  \end{lstlisting}
\end{frame}

\begin{frame}[fragile]
  \frametitle{Arithmetic operators}
  \begin{lstlisting}
In []: a = 7546

In []: a += 1
In []: a
Out[]: 7547

In []: a -= 5
In []: a

In []: a *= 2

In []: a /= 5
  \end{lstlisting}
\end{frame}

\begin{frame}[fragile]
  \frametitle{String operations}
  \begin{lstlisting}
In []: s = 'Hello'

In []: p = 'World'

In []: s + p 
Out[]: 'HelloWorld'

In []: s * 4
Out[]: 'HelloHelloHelloHello'
  \end{lstlisting}
\end{frame}

\begin{frame}[fragile]
  \frametitle{String operations \ldots}
  \begin{lstlisting}
In []: s * s
  \end{lstlisting}
  \pause
  \begin{lstlisting}
--------------------------------------------
TypeError  Traceback (most recent call last)

<ipython console> in <module>()

TypeError: can`t multiply sequence by
                non-int of type `str`
  \end{lstlisting}
\end{frame}

\begin{frame}[fragile]
  \frametitle{String methods}
  \begin{lstlisting}
In []: a = 'Hello World'
In []: a.startswith('Hell')
Out[]: True

In []: a.endswith('ld')
Out[]: True

In []: a.upper()
Out[]: 'HELLO WORLD'

In []: a.lower()
Out[]: 'hello world'
  \end{lstlisting}
\end{frame}

\begin{frame}[fragile]
\frametitle{Strings: \typ{split} \& \typ{join}}
  \begin{lstlisting}
In []: chars = 'a b c'
In []: chars.split()
Out[]: ['a', 'b', 'c']
In []: ' '.join(['a', 'b', 'c'])
Out[]: 'a b c'
  \end{lstlisting}

  \begin{lstlisting}
In []: alpha = ', '.join(['a', 'b', 'c'])
In []: alpha
Out[]: 'a, b, c'
In []: alpha.split(', ')
Out[]: ['a', 'b', 'c']
  \end{lstlisting}
\end{frame}

\begin{frame}[fragile]
\frametitle{String formatting}
  \begin{lstlisting}
In []: x, y = 1, 1.234

In []: 'x is %s, y is %s' %(x, y)
Out[]: 'x is 1, y is 1.234'
  \end{lstlisting}
  \begin{itemize}
    \item \emph{\%d}, \emph{\%f} etc. available
  \end{itemize}
  \emphbar{\url{http://docs.python.org/library/stdtypes.html}}
%%  \inctime{10}
\end{frame}

\begin{frame}[fragile]
  \frametitle{Relational and logical operators}
  \begin{lstlisting}
In []: p, z, n = 1, 0, -1
In []: p == n
Out[]: False

In []: p >= n
Out[]: True

In []: n < z < p
Out[]: True

In []: p + n != z
Out[]: False
  \end{lstlisting}
\end{frame}

\begin{frame}[fragile]
  \frametitle{Built-ins}
  \begin{lstlisting}
In []: int(17 / 2.0)
Out[]: 8

In []: float(17 / 2)
Out[]: 8.0

In []: str(17 / 2.0)
Out[]: '8.5'

In []: round( 7.5 )
Out[]: 8.0
  \end{lstlisting}
\end{frame}

\begin{frame}[fragile]
  \frametitle{Odds and ends}
  \begin{itemize}
    \item Case sensitive
    \item Dynamically typed $\Rightarrow$ need not specify a type
      \begin{lstlisting}
In []: a = 1
In []: a = 1.1
In []: a = "Now I am a string!"
      \end{lstlisting}
    \item Comments:
      \begin{lstlisting}
In []: a = 1  # In-line comments
In []: # A comment line.
In []: a = "# Not a comment!"
      \end{lstlisting}
  \end{itemize}
%%  \inctime{15}
\end{frame}

\section{Simple IO}
\begin{frame}[fragile]
  \frametitle{Simple IO: Console Input}
  \small
  \begin{itemize}
    \item raw\_input() waits for user input.
      \begin{lstlisting}
In []: a = raw_input()
5

In []: a
Out[]: '5'

In []: a = raw_input('Enter a value: ')
Enter a value: 5
      \end{lstlisting}
    \item Prompt string is optional.
    \item All keystrokes are strings!
    \item \typ{int()} converts string to int.
  \end{itemize}
\end{frame}

\begin{frame}[fragile]
  \frametitle{Simple IO: Console output}
  \begin{itemize}
    \item \typ{print} is straight forward
    \item Put the following code snippet in a file \typ{hello1.py}
  \end{itemize}
  \begin{lstlisting}
print "Hello"
print "World"


In []: %run -i hello1.py
Hello
World
  \end{lstlisting}
\end{frame}

\begin{frame}[fragile]
  \frametitle{Simple IO: Console output \ldots}
Put the following code snippet in a file \typ{hello2.py}
  \begin{lstlisting}
print "Hello",
print "World"


In []: %run -i hello2.py
Hello World
  \end{lstlisting}

\emphbar{Note the distinction between \typ{print x} and \typ{print x,}}
\end{frame}

\section{Control flow}
\begin{frame}
  \frametitle{Control flow constructs}  
  \begin{itemize}
  \item \kwrd{if/elif/else}: branching
  \item \kwrd{while}: looping
  \item \kwrd{for}: iterating
  \item \kwrd{break, continue}: modify loop 
  \item \kwrd{pass}: syntactic filler
  \end{itemize}
\end{frame}

\subsection{Basic Conditional flow}
\begin{frame}[fragile]
  \frametitle{\typ{if...elif...else} example}
Type the following code in an editor \& save as \alert{ladder.py}
  \small
  \begin{lstlisting}
x = int(raw_input("Enter an integer:"))
if x < 0:
    print 'Be positive!'
elif x == 0:
    print 'Zero'
elif x == 1:
    print 'Single'
else:
    print 'More'

  \end{lstlisting}
%%  \inctime{10}
\end{frame}

\section{Control flow}
\subsection{Basic Looping}
\begin{frame}[fragile]
  \frametitle{\typ{while}}
\begin{block}{Example: Fibonacci series}
  Sum of previous two elements defines the next
\end{block}
  \begin{lstlisting}
In []: a, b = 0, 1
In []: while b < 10:
  ...:     print b,
  ...:     a, b = b, a + b
  ...:
  ...:
\end{lstlisting}
\typ{1 1 2 3 5 8}\\
\end{frame}

\begin{frame}[fragile]
\frametitle{\typ{range()}}
\kwrd{range([start,] stop[, step])}\\
\begin{itemize}
  \item \typ{range()} returns a list of integers
  \item The \typ{start} and the \typ{step} arguments are optional
  \item \typ{stop} is not included in the list
\end{itemize}
\vspace*{.5in}
\begin{block}{Documentation convention}
  \begin{itemize}
    \item \alert{Anything within \typ{[]} is optional}
    \item Nothing to do with Python.
  \end{itemize}
\end{block}
\end{frame}

\begin{frame}[fragile]
  \frametitle{\typ{for} \ldots \typ{range()}}
Example: print squares of first \typ{5} numbers
  \begin{lstlisting}
In []: for i in range(5):
 ....:     print i, i * i
 ....:
 ....:
0 0
1 1
2 4
3 9
4 16
\end{lstlisting}
\end{frame}

\begin{frame}[fragile]
  \frametitle{\typ{for} \ldots \typ{range()}}
Example: print squares of odd numbers from 3 to 9
  \begin{lstlisting}
In []: for i in range(3, 10, 2):
 ....:     print i, i * i
 ....:
 ....:
3 9
5 25
7 49
9 81
\end{lstlisting}
%% \inctime{5}
\end{frame}

\subsection{Exercises}

\begin{frame}{Problem 1.1: \emph{Armstrong} numbers}
  Write a program that displays all three digit numbers that are equal to the sum of the cubes of their digits. That is, print numbers $abc$ that have the property $abc = a^3 + b^3 + c^3$\\
For example, $153 = 1^3 + 5^3 + 3^3$\\
\vspace*{0.2in}
\end{frame}

\begin{frame}{Problem 1.2: Collatz sequence}
\begin{enumerate}
  \item Start with an arbitrary (positive) integer. 
  \item If the number is even, divide by 2; if the number is odd, multiply by 3 and add 1.
  \item Repeat the procedure with the new number.
  \item It appears that for all starting values there is a cycle of 4, 2, 1 at which the procedure loops.
\end{enumerate}
    Write a program that accepts the starting value and prints out the Collatz sequence.
%% \inctime{5}
\end{frame}


\begin{frame}[fragile]
  \frametitle{What did we learn?}
  \begin{itemize}
    \item Data types: int, float, complex, boolean, string
    \item Operators: +, -, *, /, \%, **, +=, -=, *=, /=, >, <, <=, >=, ==, !=, a < b < c
    \item Simple IO: \kwrd{raw\_input} and \kwrd{print}
    \item Conditionals: \kwrd{if elif else}
    \item Looping: \kwrd{while} \& \kwrd{for} 
  \end{itemize}
\end{frame}

\end{document}

%% Questions for Quiz %%
%% ------------------ %%


\begin{frame}
\frametitle{\incqno }
  What is the largest integer value that can be represented natively by Python?
\end{frame}

\begin{frame}
\frametitle{\incqno }
  What is the result of 17.0 / 2?
\end{frame}

\begin{frame}
\frametitle{\incqno }
  Which of the following is not a type in Python?
  \begin{enumerate}
    \item int
    \item float
    \item char
    \item string
  \end{enumerate}
\end{frame}

\begin{frame}
\frametitle{\incqno }
How do you create a complex number with real part 2 and imaginary part
0.5.
\end{frame}

\begin{frame}
\frametitle{\incqno }
  What is the difference between \kwrd{print} \emph{x} and \kwrd{print} \emph{x,} ?
\end{frame}

\begin{frame}
\frametitle{\incqno }
  What does '*' * 40 produce?
\end{frame}

\begin{frame}[fragile]
\frametitle{\incqno }
    What is the output of:
    \begin{lstlisting}
In []: ', '.join(['a', 'b', 'c'])
    \end{lstlisting}
\end{frame}


\begin{frame}[fragile]
    \frametitle{\incqno}
  \begin{lstlisting}
In []: 47 % 3 
  \end{lstlisting}
  What is the output?
\end{frame}