diff -r 81a74c2aef61 -r 7604debe7513 advanced-features-functions.rst
--- a/advanced-features-functions.rst	Thu Sep 16 12:12:03 2010 +0530
+++ b/advanced-features-functions.rst	Thu Sep 16 17:33:31 2010 +0530
@@ -2,3 +2,202 @@
  Script
 ========
 
+{{{ show the welcome slide }}}
+
+Welcome to the tutorial on advanced feature of functions. 
+
+{{{ show the outline slide }}}
+
+In this tutorial we shall be looking at specifying default arguments
+to functions when defining them and calling functions using keyword
+arguments. We shall also, look at some of the built-in functions
+available in the standard library of Python.
+
+{{{ switch to terminal }}}
+
+We have an ``ipython`` terminal open, which we shall be using through
+out this session. 
+
+Let's use the ``round`` function as an example to understand what a
+default value of an argument means. Let's type the following
+expressions in the terminal. 
+
+::
+
+  round(2.484)
+
+  round(2.484, 2)
+
+Both the first expression and the second are calls to the ``round``
+function, but the first calls it with only one argument and the second
+calls it with two arguments. By observing the output, we can guess
+that the first one is equivalent to call with the second argument
+being 0. 0 is the default value of the argument. 
+
+{{{ show a slide with examples of functions showing default values }}}
+::
+
+  s.strip() # strips on spaces. 
+  s.strip('@') # strips the string of '@' symbols.
+
+  plot(x, y) # plots with x vs. y using default line style. 
+  plot(x, y, 'o') # plots x vs. y with circle markers. 
+
+  linspace(0, 2*pi, 100) # returns 100 points between 0 and 2pi
+  linspace(0, 2*pi) # returns 50 points between 0 and 2pi
+
+#[punch: all above content goes on to a slide]
+
+{{{ switch back to ipython }}}
+
+Let's now define a simple function that uses default arguments. We
+define a simple function that prints a welcome message to a person,
+given a greeting and his/her name.
+
+::
+
+  def welcome(greet, name="World"):
+      print greet, name
+
+Let us first call the function with two arguments, one for ``greet``
+and other for ``name``.
+
+::
+
+  welcome("Hi", "Guido")          
+
+We get the expected welcome message, "Hi Guido". 
+
+Now let us call the function with just one argument "Hello". 
+::
+
+  welcome("Hello")
+
+"Hello" is treated as the ``greet`` and we get "Hello World" as
+the output. "World" is the default value for the argument ``name``. 
+
+E%% %% Pause the video here and redefine the function ``welcome``, by
+interchanging it's arguments. Place the ``name`` argument with it's
+default value of "Hello" before the ``greet`` argument. Then, resume
+the video. 
+
+::
+
+  def welcome(name="World", greet):
+      print greet, name
+
+We get an error that reads ``SyntaxError: non-default argument follows
+default argument``. When defining a function all the argument with
+default values should come at the end. 
+
+E%% %% Pause the video here and type ``linspace?`` to see the
+definition of the command and notice how all the arguments with
+default values are towards the end.
+
+::
+
+  linspace?
+
+E%% %% Pause the video here and redefine the function ``welcome`` with
+a default value of "Hello" to the ``greet`` argument. Then, call the
+function without any arguments. Then, resume the video. 
+
+::
+
+  def welcome(greet="Hello", name="World"):
+      print greet, name
+ 
+
+  welcome()
+
+
+Let us now learn what keyword arguments are. 
+
+{{{ show a slide with examples using keyword arguments. }}}
+::
+
+  legend(['sin(2y)'], loc = 'center')
+
+  plot(y, sin(y), 'g', linewidth = 2)
+
+  annotate('local max', xy = (1.5, 1))
+
+  pie(science.values(), labels = science.keys())
+
+When you are calling functions in Python, you don't need to remember
+the order in which to pass the arguments. Instead, you can use the
+name of the argument to pass it a value. This slide shows a few
+function calls that use keyword arguments. ``loc``, ``linewidth``,
+``xy`` and ``labels`` are being called with keyword arguments. 
+
+{{{ switch to ipython terminal }}}
+
+Let us try and understand this better using the ``welcome`` function
+that we have been using all along. Let us call it in different ways
+and observe the output to see how keyword arguments work. 
+
+::
+
+  welcome()
+
+  welcome("Hello", "James")
+
+  welcome("Hi", name="Guido")
+
+When no keyword is specified, the arguments are allotted based on
+their position. So, "Hi" is the value of the argument ``greet`` and
+name is passed the value "Guido". 
+::
+
+  welcome(name="Guido", greet="Hey! ")
+
+When keyword arguments are used, the arguments can be called in any
+order. 
+
+::
+
+  welcome(name="Guido", "Hey")
+
+This call returns an error that reads, ``non keyword arg after keyword
+arg``. Python expects all the keyword to be present towards the end. 
+
+That brings us to the end of what we wanted to learn about ``keyword``
+arguments. 
+
+{{{ switch to a slide showing variety of functions with uses }}}
+
+Before defining a function of your own, make sure that you check the
+standard library, for a similar function. Python is popularly called a
+"Batteries included" language, for the huge library that comes along
+with it. 
+
+::
+
+  Math functions - abs, sin, ....
+
+#[punch: Need to decide, exactly what to put here. Reviewer comments
+ welcome.] 
+  
+
+{{{ switch to slide showing classes of functions in pylab, scipy }}}
+
+Apart from the standard library there are other libraries like ``pylab``,
+``scipy``, etc which have a huge collection of functions for scientific
+purposes. 
+::
+
+  pylab
+    plot, bar, contour, boxplot, errorbar, log, polar, quiver, semilog
+
+  scipy (modules)
+    fftpack, stats, linalg, ndimage, signal, optimize, integrate
+
+{{{ switch slide to summary slide }}}
+
+That brings us to the end of this tutorial. In this tutorial we have
+learnt how to use functions with default values and keyword
+arguments. We also looked at the range of functions available in the
+Python standard library and the Scientific Computing related
+packages. 
+
+Thank You!