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+++ b/getting-started-ipython.rst Thu Sep 16 12:10:16 2010 +0530
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+========
+ Script
+========
+
+Welcome to so and so..
+
+
+This tutorial will cover the basic usage of the ``ipython``
+interpreter. The following topics would be covered.
+
+{{{ Show slide with outline of the session. }}}
+
+IPython is an enhanced Python interpreter that provides features like
+tabcompletion, easier access to help and many other functionalities
+which are not available in the vannila Python interpreter.
+
+First let us see how to invoke the ``ipython`` interpreter.
+
+We type
+::
+
+ ipython
+
+at the terminal prompt to invoke the ipython interpreter.
+
+We get a prompt with ``In [1]:`` after getting some information about
+the version of Python installed and some help commands.
+
+If you get an error saying something like ``ipython is not
+installed``, refer to the tutorial on how to install the packages
+required for this course.
+
+Now, to quit the ipython interpreter, type Ctrl-D. You are prompted
+asking if you really want to exit, type y to say yes and quit ipython.
+
+Start ipython again, as you did before.
+
+The prompt that you have says ``In [1]``. ``In`` stands for input and the
+ipython interpreter is ready to accept input from you.
+
+Now let us see, how we can type some commands into the interpreter.
+
+Start with the simplest thing, addition.
+
+Let's type
+::
+ 1+2
+
+at the prompt. IPython promptly gives back the output as 3. Notice
+that the output is displayed with an ``Out[1]`` indication.
+
+Let's try out few other mathematical operations.
+::
+
+ 5 - 3
+ 7 - 4
+ 6 * 5
+
+Now let's ``print 1+2``. Instead of typing the whole thing, we make
+use of the fact that IPython remembers the history of the commands
+that you have already used. We use the up arrow key to go back the
+command ``1+2``. We then use the left-arrow key to navigate to the
+beginning of the line and add the word ``print`` and a space. Then hit
+enter and observe that the interpreter prints out the value as 3,
+without the Out[] indication.
+
+Now, let's change the previous command ``print 1+2`` to ``print
+10*2``. We use the up arrow again to navigate to the previous command
+and use the left arrow key to move the cursor on to the + symbol and
+then use the delete key to remove it and type 0 and * to change the
+expression to the required one. We hit enter to see the output of
+``print``.
+
+Now, let's say we want to use the function ``round``. We type ``ro``
+at the prompt and hit the tab key. As you can see, the IPython
+completes the command. This feature is called the tab-completion.
+
+Now, we remove all the characters and just type ``r`` and then hit
+tab. IPython does not complete the command since there are many
+possibilities. It just lists out all the possible completions.
+
+%% %% Pause the video here and type ``ab`` and hit tab to see what
+happens. Next, jut type ``a`` and hit tab to see what happens.
+
+``ab`` tab completes to ``abs`` and ``a<tab>`` gives us a list of all
+the commands starting with a.
+
+Now, let's see what these functions are used for. We will use the
+help features of ipython to find this out.
+
+To get the help of any function, we first type the function, ``abs``
+in our case and then add a ? at the end and hit enter.
+
+As the documentation says, ``abs`` accepts a number as an input and
+returns it's absolute value.
+
+We say,
+::
+
+ abs(-19)
+
+ abs(19)
+
+We get 19, as expected, in both the cases.
+
+Does it work for decimals (or floats)? Let's try typing abs(-10.5)
+and we do get back 10.5.
+
+%% %% Pause the video here, and look-up the documentation of ``round``
+and see how to use it.
+
+::
+
+ round?
+
+If you notice, there are extra square brackets around the ``ndigits``.
+This means that ``ndigits`` is optional and 0 is the default value.
+Optional parameters are shown in square brackets anywhere in Python
+documentation.
+
+The function ``round``, rounds a number to a given precision.
+
+%% %% Pause the video here and check the output of
+round(2.48)
+round(2.48, 1)
+round(2.48, 2)
+and then resume the video.
+
+::
+ round(2.484)
+ round(2.484, 1)
+ round(2.484, 2)
+
+We get 2.0, 2.5 and 2.48, which are what we expect.
+
+Let's now see how to correct typing errors that we make when typing at
+the terminal. As already shown, if we haven't hit the enter key
+already, we could navigate using the arrow keys and make deletions
+using delete or backspace key and correct the errors.
+
+Let's now type round(2.484 and hit enter, without closing the
+parenthesis. We get a prompt with dots. This prompt is the
+continuation prompt of ``ipython``. It appears, the previous line is
+incomplete in some way. We now complete the command by typing, the
+closing parenthesis and hitting enter. We get the expected output of
+2.5.
+
+In other instances, if we commit a typing error with a longer and more
+complex expression and end up with the continuation prompt, we can
+type Ctrl-C to interrupt the command and get back the ``ipython`` input
+prompt.
+
+%% %% Pause the video here.
+Try typing round(2.484, and hit enter. and then cancel the command
+using Ctrl-C. Then, type the command, round(2.484, 2) and resume the
+video.
+
+::
+
+ round(2.484
+ ^C
+
+ round(2.484, 2)
+
+This brings us to the end of the tutorial on getting started with
+``ipython``.
+
+In this tutorial we have seen
+{{{ show the outline/summary slide. }}}
+
+Thank you!
+
+
+