Add exceptions and practice exercises.

Update makefile.

3 files changed, 502 insertions, 1 deletions

diff --git a/basic_python/Makefile b/basic_python/Makefile
index 1cdc572..6310d3a 100644
--- a/basic_python/Makefile
+++ b/basic_python/Makefile
@@ -9,7 +9,13 @@ SLIDES= basics.pdf \
   control_flow.pdf \
   practice_control_flow.pdf \
   core_data_structures.pdf \
-  practice_ds.pdf
+  practice_ds.pdf \
+  functions.pdf \
+  practice_functions.pdf \
+  modules.pdf \
+  files.pdf \
+  exceptions.pdf \
+  practice_files_exc.pdf
 
 all: 	$(SLIDES)
 
diff --git a/basic_python/exceptions.tex b/basic_python/exceptions.tex
new file mode 100644
index 0000000..766dc98
--- /dev/null
+++ b/basic_python/exceptions.tex
@@ -0,0 +1,289 @@
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%Tutorial slides on Python.
+%
+% Author: FOSSEE
+% Copyright (c) 2017, FOSSEE, IIT Bombay
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+\documentclass[14pt,compress]{beamer}
+\input{macros.tex}
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% Title page
+\title[Exceptions]{Python language: exceptions}
+
+\author[FOSSEE Team] {The FOSSEE Group}
+
+\institute[IIT Bombay] {Department of Aerospace Engineering\\IIT Bombay}
+\date[] {Mumbai, India}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% DOCUMENT STARTS
+\begin{document}
+
+\begin{frame}
+  \titlepage
+\end{frame}
+
+\begin{frame}{Motivation}
+    \begin{itemize}
+        \item How do you signal errors to a user?
+    \end{itemize}
+\end{frame}
+
+\begin{frame}
+  \frametitle{Exceptions}
+  \begin{itemize}
+  \item Python's way of notifying you of errors
+  \item Several standard exceptions: \texttt{SyntaxError}, \texttt{IOError}
+    etc.
+  \item Users can also \texttt{raise} errors
+  \item Users can create their own exceptions
+  \item Exceptions can be ``caught'' via \texttt{try/except} blocks
+  \end{itemize}
+\end{frame}
+
+\begin{frame}[fragile]
+ \frametitle{Exceptions: examples}
+ \begin{lstlisting}
+In []: while True print('Hello world')
+ \end{lstlisting}
+\pause
+  \begin{lstlisting}
+File "<stdin>", line 1, in ?
+    while True print('Hello world')
+                   ^
+SyntaxError: invalid syntax
+\end{lstlisting}
+\end{frame}
+
+\begin{frame}[fragile]
+ \frametitle{Exceptions: examples}
+ \begin{lstlisting}
+In []: print(spam)
+\end{lstlisting}
+\pause
+\begin{lstlisting}
+Traceback (most recent call last):
+  File "<stdin>", line 1, in <module>
+NameError: name 'spam' is not defined
+\end{lstlisting}
+\end{frame}
+
+\begin{frame}[fragile]
+ \frametitle{Exceptions: examples}
+ \begin{lstlisting}
+In []: 1 / 0
+\end{lstlisting}
+\pause
+\begin{lstlisting}
+Traceback (most recent call last):
+  File "<stdin>", line 1, in <module>
+ZeroDivisionError: integer division
+or modulo by zero
+\end{lstlisting}
+\end{frame}
+
+
+\begin{frame}[fragile]
+  \frametitle{Exceptions: examples}
+\begin{lstlisting}
+In []: '2' + 2
+\end{lstlisting}
+\pause
+\begin{lstlisting}
+Traceback (most recent call last):
+  File "<stdin>", line 1, in ?
+TypeError: cannot concatenate 'str' and 'int' objects
+\end{lstlisting}
+\end{frame}
+
+
+\begin{frame}[fragile]
+  \frametitle{Processing user input}
+  \begin{lstlisting}
+prompt = 'Enter a number(Q to quit): '
+a = input(prompt)
+
+num = int(a) if a != 'Q' else 0
+  \end{lstlisting}
+  \emphbar{What if the user enters some other alphabet?}
+\end{frame}
+
+
+\begin{frame}[fragile]
+  \frametitle{Handling Exceptions}
+  Python provides a \typ{try} and \typ{except} clause.
+  \begin{lstlisting}
+prompt = 'Enter a number(Q to quit): '
+a = input(prompt)
+try:
+    num = int(a)
+    print(num)
+except:
+    if a == 'Q':
+        print("Exiting ...")
+    else:
+        print("Wrong input ...")
+  \end{lstlisting}
+\end{frame}
+
+\begin{frame}[fragile]
+  \frametitle{Handling Exceptions a little better}
+  Use specific exceptions; avoid blanket except clauses
+  \begin{lstlisting}
+prompt = 'Enter a number(Q to quit): '
+a = input(prompt)
+try:
+    num = int(a)
+    print(num)
+except ValueError:
+    if a == 'Q':
+        print("Exiting ...")
+    else:
+        print("Wrong input ...")
+  \end{lstlisting}
+\end{frame}
+
+
+\begin{frame}[fragile]
+  \frametitle{Exceptions: examples}
+  \small
+\begin{lstlisting}
+prompt = "Enter a number: "
+while True:
+    try:
+        x = int(input(prompt))
+        break
+    except ValueError:
+        print("Invalid input, try again...")
+
+\end{lstlisting}
+\end{frame}
+
+\begin{frame}[fragile]
+  \frametitle{Catching multiple exceptions}
+\begin{lstlisting}
+data = input()
+try:
+    x = int(data.split(',')[1])
+    break
+except IndexError:
+    print('Input at least 2 values.')
+except ValueError:
+    print("Invalid input, try again...")
+
+\end{lstlisting}
+\end{frame}
+
+
+\begin{frame}[fragile]
+  \frametitle{Catching multiple exceptions}
+\begin{lstlisting}
+data = input()
+try:
+    x = int(data.split(',')[1])
+    break
+except (ValueError, IndexError):
+    print("Invalid input ...")
+
+\end{lstlisting}
+\end{frame}
+
+\begin{frame}[fragile]
+  \frametitle{\typ{try, except, else}}
+\begin{lstlisting}
+data = input()
+try:
+    x = int(data.split(',')[1])
+    break
+except (ValueError, IndexError):
+    print("Invalid input ...")
+else:
+    print('All is well!')
+  \end{lstlisting}
+
+\end{frame}
+
+
+\begin{frame}
+  \frametitle{Some comments}
+  \begin{itemize}
+  \item In practice NEVER use blanket except clauses
+  \item Always catch specific exceptions
+  \end{itemize}
+\end{frame}
+
+\begin{frame}[fragile]
+  \frametitle{Exceptions: raising your exceptions}
+\small
+\begin{lstlisting}
+>>> raise ValueError("your error message")
+Traceback (most recent call last):
+  File "<stdin>", line 2, in ?
+ValueError: your error message
+\end{lstlisting}
+\end{frame}
+
+
+
+\begin{frame}[fragile]
+  \frametitle{Exceptions: try/finally}
+  \small
+\begin{lstlisting}
+while True:
+    try:
+        x = int(input(prompt))
+        break
+    except ValueError:
+        print("Invalid number, try again...")
+    finally:
+        print "All good!"
+
+      \end{lstlisting}
+      \normalsize
+      Always runs the finally clause!
+\end{frame}
+
+
+\begin{frame}[fragile]
+  \frametitle{Exceptions: try/finally}
+  \begin{lstlisting}
+def f(x):
+    try:
+        y = int(x)
+        return y
+    except ValueError:
+        print(x)
+    finally:
+        print('finally')
+
+>>> f(1)
+>>> f('a')
+\end{lstlisting}
+Always runs the finally clause!
+\end{frame}
+
+
+\begin{frame}
+  \frametitle{Summary}
+  \begin{itemize}
+  \item Catching exceptions with \typ{try/except}
+  \item Catching multiple exceptions
+  \item Cleanup with \typ{finally}
+  \item Raising your own exceptions
+  \end{itemize}
+\end{frame}
+
+\begin{frame}
+  \frametitle{What next?}
+  \begin{itemize}
+  \item Only covered the very basics
+  \item More advanced topics remain
+  \item Read the official Python tutorial:
+    \url{docs.python.org/tutorial/}
+  \end{itemize}
+\end{frame}
+
+\end{document}
diff --git a/basic_python/practice_files_exc.tex b/basic_python/practice_files_exc.tex
new file mode 100644
index 0000000..4a7cdfc
--- /dev/null
+++ b/basic_python/practice_files_exc.tex
@@ -0,0 +1,206 @@
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% Tutorial slides on Python.
+%
+% Author: FOSSEE
+% Copyright (c) 2017, FOSSEE, IIT Bombay
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+\documentclass[14pt,compress]{beamer}
+
+\input{macros.tex}
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% Title page
+\title[Files/exceptions]{Practice exercises: files and exceptions}
+
+\author[FOSSEE Team] {The FOSSEE Group}
+
+\institute[FOSSEE -- IITB] {Department of Aerospace Engineering\\IIT Bombay}
+\date[] {Mumbai, India}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% DOCUMENT STARTS
+\begin{document}
+
+\begin{frame}
+  \titlepage
+\end{frame}
+
+
+\begin{frame}[plain]
+  \frametitle{Exercise: reading from a file}
+  \begin{enumerate}
+  \item Define a function called \typ{largest} which takes a single argument
+  \item The argument passed will be an opened file object
+  \item Read the data in the file
+  \item Assume that the data is separated by spaces and are all numbers
+  \item Find the maximum value in the file
+  \item Do not use \typ{loadtxt}!
+  \end{enumerate}
+\end{frame}
+
+\begin{frame}[fragile,plain]
+\frametitle{Solution}
+\begin{lstlisting}
+  def largest(f):
+      data = []
+      for line in f:
+          for field in line.split():
+              data.append(float(field))
+      return max(data)
+
+\end{lstlisting}
+\end{frame}
+
+\begin{frame}[fragile,plain]
+\frametitle{Another solution}
+\begin{lstlisting}
+def largest(f):
+    res = -1e20
+    for line in f:
+        for field in line.split():
+            res = max(res, float(field))
+    return res
+
+\end{lstlisting}
+\end{frame}
+
+
+\begin{frame}[plain]
+  \frametitle{Exercise: reading/writing files}
+  \begin{enumerate}
+  \item Read the \typ{pendulum.txt} file
+  \item Print the second column alone to another file called \typ{col2.txt}
+  \item Remember to add a newline
+  \end{enumerate}
+\end{frame}
+
+\begin{frame}[fragile,plain]
+\frametitle{Solution}
+\begin{lstlisting}
+  f = open('pendulum.txt')
+  out = open('col2.txt', 'w')
+  for line in f:
+      fields = line.split()
+      out.write(fields[1] + '\n')
+  f.close()
+  out.close()
+\end{lstlisting}
+\end{frame}
+
+\begin{frame}[fragile,plain]
+\frametitle{Another solution}
+\begin{lstlisting}
+  f = open('pendulum.txt')
+  out = open('col2.txt', 'w')
+  for line in f:
+      fields = line.split()
+      print(fields[1], file=out)
+  f.close()
+  out.close()
+\end{lstlisting}
+\end{frame}
+
+\begin{frame}[plain, fragile]
+  \frametitle{Exercise: simple exceptions}
+  \begin{enumerate}
+  \item Write a function called \typ{my\_sum}
+  \item The function is passed a single string with terms separated by spaces
+  \item The string contains both names and integer values in arbitrary order
+  \item Find the sum of all the numbers in the string
+  \end{enumerate}
+  For example:
+  \begin{lstlisting}
+>>> my_sum('1 fox, 2 dogs and 3 jackals')
+6
+>>> my_sum('3 blind mice and 1 man')
+4
+  \end{lstlisting}
+\end{frame}
+
+\begin{frame}[fragile,plain]
+\frametitle{Possible solution}
+\begin{lstlisting}
+  def my_sum(s):
+      total = 0
+      for word in s.split():
+          try:
+              total += int(word)
+          except ValueError:
+              pass
+      return total
+ \end{lstlisting}
+\end{frame}
+
+\begin{frame}[plain, fragile]
+  \frametitle{Exercise: catching exceptions}
+  \small
+  \begin{enumerate}
+  \item Write a function called \typ{safe\_run(f, x)}
+  \item \typ{f} is a function and \typ{x} is a value
+  \item \typ{f} can raise either \typ{ValueError} or \typ{TypeError}
+  \item Your function should return \typ{'OK'} if no exception is raised
+  \item Return \typ{'ValueError'} if \typ{ValueError} is raised
+  \item Return \typ{'TypeError'} if \typ{TypeError} is raised
+  \end{enumerate}
+  For example:
+  \begin{lstlisting}
+    >>> safe_run(float, 'A')
+    'ValueError'
+    >>> def f(x): return x + 2
+    >>> safe_run(f, '2')
+    'TypeError'
+    >>> safe_run(float, '2')
+    'OK'
+  \end{lstlisting}
+
+\end{frame}
+
+\begin{frame}[fragile,plain]
+\frametitle{Possible solution}
+\begin{lstlisting}
+  def safe_run(f, x):
+      try:
+          f(x)
+      except ValueError:
+          return 'ValueError'
+      except TypeError:
+          return 'TypeError'
+      else:
+          return 'OK'
+
+ \end{lstlisting}
+\end{frame}
+
+\begin{frame}[plain, fragile]
+  \frametitle{Exercise: raising exceptions}
+  \begin{enumerate}
+  \item Write a function \typ{func} which takes a single integer argument
+  \item If \typ{x} is not a positive integer raise a \typ{ValueError}
+  \item If \typ{x} is not an integer type raise a \typ{TypeError}
+  \end{enumerate}
+\end{frame}
+
+\begin{frame}[fragile,plain]
+  \frametitle{Possible solution}
+  \small
+\begin{lstlisting}
+  def func(x):
+      if type(x) != int:
+          raise TypeError('Expected int')
+      elif x < 0:
+          raise ValueError('Got negative int')
+
+\end{lstlisting}
+\end{frame}
+
+\begin{frame}
+  \centering
+  \Huge
+
+  Thank you!
+\end{frame}
+\end{document}
+
+\end{document}