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-\section{Strings}
-
-\begin{frame}[fragile]
- \frametitle{What are Strings?}
- \begin{itemize}
- \item Anything quoted is a string
- \item Single quotes, double quotes or triple single/double quotes
- \item Any length --- single character, null string, \ldots
- \end{itemize}
- \begin{lstlisting}
- In[]: 'This is a string'
- In[]: "This is a string too'
- In[]: '''This is a string as well'''
- In[]: """This is also a string"""
- In[]: '' # empty string
- \end{lstlisting}
-\end{frame}
-
-\begin{frame}[fragile]
- \frametitle{Why so many?}
- \begin{itemize}
- \item Reduce the need for escaping
- \end{itemize}
- \begin{lstlisting}
- In[]: "Python's strings are powerful!"
- In[]: 'He said, "I love Python!"'
- \end{lstlisting}
- \begin{itemize}
- \item Triple quoted strings can be multi-line
- \item Used for doc-strings
- \end{itemize}
-\end{frame}
-
-\begin{frame}[fragile]
- \frametitle{Assignment \& Operations}
- \begin{lstlisting}
- In[]: a = 'Hello'
- In[]: b = 'World'
- In[]: c = a + ', ' + b + '!'
- \end{lstlisting}
- \begin{itemize}
- \item Strings can be multiplied with numbers
- \end{itemize}
- \begin{lstlisting}
- In[]: a = 'Hello'
- In[]: a * 5
- \end{lstlisting}
-\end{frame}
-
-\begin{frame}[fragile]
- \frametitle{Accessing Elements}
- \begin{lstlisting}
- In[]: print a[0], a[4], a[-1], a[-4]
- \end{lstlisting}
- \begin{itemize}
- \item Can we change the elements?
- \end{itemize}
- \begin{lstlisting}
- In[]: a[0] = 'H'
- \end{lstlisting}
- \begin{itemize}
- \item Strings are immutable!
- \end{itemize}
-\end{frame}
-
-\begin{frame}[fragile]
- \frametitle{Problem - Day of the Week?}
- \begin{itemize}
- \item Strings have methods to manipulate them
- \end{itemize}
- \begin{block}{Problem}
- Given a list, \texttt{week}, containing names of the days of the
- week and a string \texttt{s}, check if the string is a day of the
- week. We should be able to check for any of the forms like,
- \emph{sat, saturday, Sat, Saturday, SAT, SATURDAY}
- \end{block}
- \begin{itemize}
- \item Get the first 3 characters of the string
- \item Convert it all to lower case
- \item Check for existence in the list, \texttt{week}
- \end{itemize}
-\end{frame}
-
-\begin{frame}[fragile]
- \frametitle{Slicing}
- \begin{lstlisting}
- In[]: q = "Hello World"
- In[]: q[0:3]
- In[]: q[:3]
- In[]: q[3:]
- In[]: q[:]
- In[]: q[-1:1]
- In[]: q[1:-1]
- \end{lstlisting}
- \begin{itemize}
- \item One or both of the limits, is optional
- \end{itemize}
-\end{frame}
-
-\begin{frame}[fragile]
- \frametitle{Striding}
- \begin{lstlisting}
- In[]: q[0:5:1]
- In[]: q[0:5:2]
- In[]: q[0:5:3]
- In[]: q[0::2]
- In[]: q[2::2]
- In[]: q[::2]
- In[]: q[5:0:-1]
- In[]: q[::-1]
- \end{lstlisting}
-\end{frame}
-
-\begin{frame}[fragile]
- \frametitle{String Methods}
- \begin{lstlisting}
- In[]: s.lower()
- In[]: s.upper()
- s.<TAB>
- \end{lstlisting}
- \begin{itemize}
- \item \alert{Strings are immutable!}
- \item A new string is being returned
- \end{itemize}
-\end{frame}
-
-\begin{frame}[fragile]
- \frametitle{Solution - Day of the Week?}
- \begin{lstlisting}
- In[]: s.lower()[:3] in week
- \end{lstlisting}
- OR
- \begin{lstlisting}
- In[]: s[:3].lower() in week
- \end{lstlisting}
-\end{frame}
-
-\begin{frame}[fragile]
- \frametitle{\texttt{join} a list of strings}
- \begin{itemize}
- \item Given a list of strings
- \item We wish to join them into a single string
- \item Possibly, each string separated by a common token
- \end{itemize}
- \begin{lstlisting}
- In[]: email_list = ["info@fossee.in",
- "enquiries@fossee.in",
- "help@fossee.in"]
- \end{lstlisting}
- \begin{lstlisting}
- In[]: '; '.join(email_list)
- In[]: ', '.join(email_list)
- \end{lstlisting}
-\end{frame}
-
-\section{Conditionals}
-
-\begin{frame}[fragile]
- \frametitle{\texttt{if-else} block}
- \begin{lstlisting}
- In[]: a = 5
- In[]: if a % 2 == 0:
- ....: print "Even"
- ....: else:
- ....: print "Odd"
- \end{lstlisting}
- \begin{itemize}
- \item A code block -- \texttt{:} and indentation
- \item Exactly one block gets executed in the \texttt{if-else}
- \end{itemize}
-\end{frame}
-
-
-\begin{frame}[fragile]
- \frametitle{\texttt{if-elif-else}}
- \begin{lstlisting}
- In[]: if a > 0:
- ....: print "positive"
- ....: elif a < 0:
- ....: print "negative"
- ....: else:
- ....: print "zero"
- \end{lstlisting}
- \begin{itemize}
- \item Only one block gets executed, depending on \texttt{a}
- \end{itemize}
-\end{frame}
-
-\begin{frame}[fragile]
- \frametitle{\texttt{else} is optional}
- \begin{lstlisting}
- In[]: if user == 'admin':
- ....: admin_Operations()
- ....: elif user == 'moderator':
- ....: moderator_operations()
- ....: elif user == 'client':
- ....: customer_operations()
- \end{lstlisting}
- \begin{itemize}
- \item Note that there is no \texttt{else} block
- \end{itemize}
-\end{frame}
-
-\begin{frame}[fragile]
- \frametitle{Ternary operator}
- \begin{itemize}
- \item \texttt{score\_str} is either \texttt{'AA'} or a string of one
- of the numbers in the range 0 to 100.
- \item We wish to convert the string to a number using \texttt{int}
- \item Convert it to 0, when it is \texttt{'AA'}
- \item \texttt{if-else} construct or the ternary operator
- \end{itemize}
- \begin{lstlisting}
- In[]: if score_str != 'AA':
- ....: score = int(score_str)
- ....: else:
- ....: score = 0
- \end{lstlisting}
- \begin{lstlisting}
- In[]: ss = score_str
- In[]: score = int(ss) if ss != 'AA' else 0
- \end{lstlisting}
-\end{frame}
-
-
-\begin{frame}[fragile]
- \frametitle{\texttt{pass}}
- \begin{itemize}
- \item \texttt{pass} is a syntactic filler
- \item When a certain block has no statements, a \texttt{pass} is
- thrown in
- \item Mostly, when you want to get back to that part, later.
- \end{itemize}
-\end{frame}
-
-\section{Loops}
-
-\begin{frame}[fragile]
- \frametitle{\texttt{while}}
- \begin{itemize}
- \item Print squares of all odd numbers less than 10 using
- \texttt{while}
- \end{itemize}
- \begin{lstlisting}
- In[]: i = 1
-
- In[]: while i<10:
- ....: print i*i
- ....: i += 2
- \end{lstlisting}
- \begin{itemize}
- \item The loops runs as long as the condition is \texttt{True}
- \end{itemize}
-\end{frame}
-
-\begin{frame}[fragile]
- \frametitle{\texttt{for}}
- \begin{itemize}
- \item Print squares of all odd numbers less than 10 using
- \texttt{for}
- \end{itemize}
- \begin{lstlisting}
- In[]: for n in [1, 2, 3]:
- ....: print n
- \end{lstlisting}
- \begin{itemize}
- \item \texttt{for} iterates over each element of a sequence
- \end{itemize}
- \begin{lstlisting}
- In[]: for n in [1, 3, 5, 7, 9]:
- ....: print n*n
-
- In[]: for n in range(1, 10, 2):
- ....: print n*n
- \end{lstlisting}
- \begin{itemize}
- \item \alert{range([start,] stop[, step])}
- \item Returns a list; Stop value is not included.
- \end{itemize}
-\end{frame}
-
-
-\begin{frame}[fragile]
- \frametitle{\texttt{break}}
- \begin{itemize}
- \item breaks out of the innermost loop.
- \item Squares of odd numbers below 10 using \texttt{while} \&
- \texttt{break}
- \end{itemize}
- \begin{lstlisting}
- In[]: i = 1
-
- In[]: while True:
- ....: print i*i
- ....: i += 2
- ....: if i>10:
- ....: break
- \end{lstlisting}
-\end{frame}
-
-\begin{frame}[fragile]
- \frametitle{\texttt{continue}}
- \begin{itemize}
- \item Skips execution of rest of the loop on current iteration
- \item Jumps to the end of this iteration
- \item Squares of all odd numbers below 10, not multiples of 3
- \end{itemize}
- \begin{lstlisting}
- In[]: for n in range(1, 10, 2):
- ....: if n%3 == 0:
- ....: continue
- ....: print n*n
- \end{lstlisting}
-\end{frame}
-
-
-\section{Lists}
-
-\begin{frame}[fragile]
- \frametitle{Creating Lists}
- \begin{lstlisting}
- In[]: empty = []
-
- In[]: p = ['spam', 'eggs', 100, 1.234]
- In[]: q = [[4, 2, 3, 4], 'and', 1, 2, 3, 4]
- \end{lstlisting}
- \begin{itemize}
- \item Lists can be empty, with no elements in them
- \item Lists can be heterogeneous -- every element of different kind
- \end{itemize}
-\end{frame}
-
-\begin{frame}[fragile]
- \frametitle{Accessing Elements}
- \begin{lstlisting}
- In[]: print p[0], p[1], p[3]
-
- In[]: print p[-1], p[-2], p[-4]
- In[]: print p[10]
- \end{lstlisting}
- \begin{itemize}
- \item Indexing starts from 0
- \item Indexes can be negative
- \item Indexes should be in the valid range
- \end{itemize}
-\end{frame}
-
-\begin{frame}[fragile]
- \frametitle{Accessing Elements \& length}
- \begin{lstlisting}
- In[]: print p[0], p[1], p[3]
-
- In[]: print p[-1], p[-2], p[-4]
- In[]: print len(p)
- In[]: print p[10]
- \end{lstlisting}
- \begin{itemize}
- \item Indexing starts from 0
- \item Indexes can be negative
- \item Indexes should be within the \texttt{range(0, len(p))}
- \end{itemize}
-\end{frame}
-
-
-\begin{frame}[fragile]
- \frametitle{Adding \& Removing Elements}
- \begin{itemize}
- \item The append method adds elements to the end of the list
- \end{itemize}
- \begin{lstlisting}
- In[]: p.append('onemore')
- In[]: p
- In[]: p.append([1, 6])
- In[]: p
- \end{lstlisting}
- \begin{itemize}
- \item Elements can be removed based on their index OR
- \item based on the value of the element
- \end{itemize}
- \begin{lstlisting}
- In[]: del p[1]
- In[]: p.remove(100)
- \end{lstlisting}
- \begin{itemize}
- \item \alert{When removing by value, first element is removed}
- \end{itemize}
-\end{frame}
-
-
-\begin{frame}[fragile]
- \frametitle{Concatenating lists}
- \begin{lstlisting}
- In[]: a = [1, 2, 3, 4]
- In[]: b = [4, 5, 6, 7]
- In[]: a + b
- In[]: print a+b, a, b
- \end{lstlisting}
- \begin{itemize}
- \item A new list is returned; None of the original lists change
- \end{itemize}
- \begin{lstlisting}
- In[]: c = a + b
- In[]: c
- \end{lstlisting}
-\end{frame}
-
-\begin{frame}[fragile]
- \frametitle{Slicing \& Striding}
- \begin{lstlisting}
- In[]: primes = [2, 3, 5, 7, 11, 13, 17, 19, 23, 29]
- In[]: primes[4:8]
- In[]: primes[:4]
-
- In[]: num = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13]
- In[]: num[1:10:2]
- In[]: num[:10]
- In[]: num[10:]
- In[]: num[::2]
- In[]: num[::-1]
- \end{lstlisting}
-\end{frame}
-
-\begin{frame}[fragile]
- \frametitle{Sorting}
- \begin{lstlisting}
- In[]: a = [5, 1, 6, 7, 7, 10]
- In[]: a.sort()
- In[]: a
- \end{lstlisting}
- \begin{itemize}
- \item \texttt{sort} method sorts the list in-place
- \item Use \texttt{sorted} if you require a new list
- \end{itemize}
- \begin{lstlisting}
- In[]: a = [5, 1, 6, 7, 7, 10]
- In[]: sorted(a)
- In[]: a
- \end{lstlisting}
-\end{frame}
-
-\begin{frame}[fragile]
- \frametitle{Reversing}
- \begin{lstlisting}
- In[]: a = [5, 1, 6, 7, 7, 10]
- In[]: a.reverse()
- In[]: a
- \end{lstlisting}
- \begin{itemize}
- \item \texttt{reverse} method reverses the list in-place
- \item Use \texttt{[::-1]} if you require a new list
- \end{itemize}
- \begin{lstlisting}
- In[]: a = [5, 1, 6, 7, 7, 10]
- In[]: a[::-1]
- In[]: a
- \end{lstlisting}
-\end{frame}
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