--- a/getting-started-with-for/script.rst Wed Nov 17 23:24:57 2010 +0530
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,308 +0,0 @@
-.. Objectives
-.. ----------
-
-.. At the end of this tutorial, you will be able to
-
-.. 1. Write blocks of code in python.
-.. #. Use for loop.
-.. #. Use ``range()`` function.
-.. #. Write blocks in python interpreter
-.. #. Write blocks in ipython interpreter.
-
-
-.. Prerequisites
-.. -------------
-
-.. 1. should have ``ipython`` and ``pylab`` installed.
-.. #. getting started with ``ipython``.
-.. #. getting started with lists.
-
-
-.. Author : Anoop Jacob Thomas <anoop@fossee.in>
- Internal Reviewer : Nishanth
- Internal Reviewer(2): Amit
- External Reviewer :
- Language Reviewer : Bhanukiran
- Checklist OK? : <10-11-2010, Anand, OK> [2010-10-05]
-
-
-=============================
-Getting started with for loop
-=============================
-
-{{{ show welcome slide }}}
-
-Hello and welcome to the tutorial `Getting started with ``for`` loop`.
-
-{{{ switch to next slide, outline slide }}}
-
-In this tutorial we will learn about ``for`` loops in python, and also
-learn how to write blocks of code in Python.
-
-.. #[Nishanth]: Instead of saying basics of indenting code,
- say How to define code blocks in Python
-
-{{{ switch to next slide, about whitespaces }}}
-
-In Python whitespace is significant, and the blocks are visually
-separated.
-
-.. #[nishanth]: Simply tell how blocks are defined in python.
- The details like braces are not used and its
- advantages like neat code can be told after completely
- explaining the indentation
-
-.. #[Amit]: Do you want to do that here. May be its better to talk about
- this after some initiation into the idea of blocks.
-
-The best practice is to indent the code using four spaces.
-
-.. #[Nishanth]: Even this detail may be skipped. Simply say use 4 spaces
- for indentation. Do that while typing so that they can
- actually see what is being typed.
-
-As you can see in the slide, ``Block B`` is an inner block and it is
-indented using 4 spaces, and after ``Block B`` the next statement in
-``Block A`` starts from the same indentation level of other ``Block
-A`` statements.
-
-Now let us move straight into ``for`` loop.
-
-{{{ switch to next slide, problem statement of exercise 1 }}}
-
-
-Write a for loop which iterates through a list of numbers and find the
-square root of each number.
-::
-
- numbers are 1369, 7225, 3364, 7056, 5625, 729, 7056, 576, 2916
-
-.. #[nishanth]: making new list with square roots induces extra complication
- like appending which has no use case here
-
-.. #[Nishanth]: The problem focuses more on square root and creation
- of list. The problem must be simple and focusing on
- nothing more but the indentation and for loop.
- May be change the problem to print squares than to
- print square roots.
-
-For the problem, first we need to create a ``list`` of numbers and
-then iterate over the list and find the square root of each element in
-it. And let us create a script, rather than typing it out in the
-interpreter itself. Create a script called list_roots.py and type the
-following.
-
-{{{ open the text editor and paste the following code there }}}
-::
-
- numbers = [1369, 7225, 3364, 7056, 5625, 729, 7056, 576, 2916]
- for each in numbers:
- print "Square root of", each, "is", sqrt(each)
- print "This is not in for loop!"
-
-.. numbers = [1, 12, 3, 4, 21, 17]
- for each in numbers:
- print each, each * each
-
-.. #[nishanth]: I don't see a use case to append the sq_root to
- square_roots. It is only complicating stuff.
- Simply iterate and print.
-
-{{{ switch to next slide, save and run script }}}
-
-{{{ save the script }}}
-
-Now save the script, and run it from your IPython interpreter. I
-assume that you have started your IPython interpreter using ``-pylab``
-option.
-
-Run the script as,
-::
-
- %run -i list_roots.py
-
-.. #[Nishanth]: you don't have to use the -i option here
-
-{{{ run the script }}}
-
-So that was easy! All what we did was iterate over the list element by
-element and then use the element for calculation. Note that here we
-used two variables. One the variable ``numbers``, which is a list,
-another one ``each``, which is the element of list under consideration
-in each cycle of the ``for`` loop. The variable names can be chosen by
-you.
-
-.. #[Nishanth]: The details like we didn't have to find the length
- are relevant for people who have programmed in C or
- other languages earlier. But for a newbie it is more
- of confusing extra info. That part may be skipped.
- Simply go ahead and focus on the syntax of for loop.
- And how the variable name is used inside the for loop.
- If you modify the question to only print, the extra
- variable sq_root can also be avoided. let it be more
- about "each", "numbers" and "for". no other new names.
-
-{{{ show the script which was created }}}
-
-Note that the lines after ``for`` statement, is indented using four
-spaces.
-
-{{{ highlight the line after for statement }}}
-
-It means that line is part of the for loop. And it is a block of code,
-although it is only a single statement in the block. And the fourth
-line or the immediate line after the ``for`` block is not indented,
-
-{{{ highlight the fourth line - the line just after for loop }}}
-
-it means that it is not part of the ``for`` loop and the lines after
-that doesn't fall in the scope of the ``for`` loop. Thus each block is
-separated by the indentation level and that marks the importance of
-white-spaces in Python.
-
-{{{ switch to the slide which shows the problem statement of the first
-problem to be tried out }}}
-
-Now a question for you to try, from the given numbers make a list of
-perfect squares and a list of those which are not. The numbers are,
-::
-
- 7225, 3268, 3364, 2966, 7056, 5625, 729, 5547, 7056, 576, 2916
-
-Pause here and try to solve the problem before proceeding further.
-
-{{{ switch to next slide, problem statement of second problem in
-solved exercise}}}
-
-Now let us try a simple one, to print the square root of numbers in
-the list. And this time let us do it right in the IPython
-interpreter.
-
-{{{ switch to next slide, Indentation in ``ipython`` }}}
-
-{{{ switch focus to the IPython interpreter }}}
-
-So let us start with making a list. Type the following
-::
-
- numbers = [1369, 7225, 3364, 7056, 5625, 729, 7056, 576, 2916]
- for each in numbers:
-
-and now you will notice that, as soon as you press the return key
-after for statement, the prompt changes to four dots and the cursor is
-not right after the four dots but there are four spaces from the
-dots. Please note that IPython automatically indents the block. The
-four dots tell you that you are inside a block. Now type the rest of
-the ``for`` loop,
-
-{{{ switch to next slide, Indentation in ``ipython`` (cont'd) }}}
-
-.. #[Nishanth]: Tell that IPython does auto indentation.
-
-::
-
- print "Square root of", each,
- print "is", sqrt(each)
-
-Now we have finished the statements in the block, and still the
-interpreter is showing four dots, this means that you are still inside the
-block. To exit from the block press the return key or the enter key twice
-without entering anything else. It printed the square root of each
-number in the list, and that is executed in a ``for`` loop.
-
-{{{ switch to next slide, Indentation in ``python`` interpreter }}}
-
-Now, let us find the cube of all the numbers from one to ten. But this
-time let us try it in the vanilla version of Python interpreter.
-
-Start the vanilla version of Python interpreter by issuing the command
-``python`` in your terminal.
-
-{{{ open the python interpreter in the terminal using the command
-python to start the vanilla Python interpreter }}}
-
-{{{ switch to next slide, Indentation in ``python`` interpreter
-(cont'd) }}}
-
-Start with,
-::
-
- for i in range(1,11):
-
-and press enter once, and we will see that this time it shows four
-dots, but the cursor is close to the dots, so we have to indent the
-block. The vanilla version of Python interpreter does not indent the
-code automatically. So enter four spaces there and then type the
-following
-::
-
- print i, "cube is", i**3
-
-Now when we hit enter, we still see the four dots, to get out of the
-block, hit enter once again
-
-.. #[Nishanth]: Here also the overhead on print can be reduced.
- Think of a simple print statement. This statement
- will be confusing for a newbie.
- We can focus more on indentation in python.
-
-.. #[nishanth]: Not sure if you must use range here. You can
- define a list of numbers and iterate on it.
- Then say this list can also be generated using
- the range function and hence introduce range.
-
-{{{ switch to the next slide, ``range()`` function }}}
-
-Okay! so the main thing that we learned here is how to use Python
-interpreter and IPython interpreter to specify blocks. But while we
-were generating the multiplication table we used something new,
-``range()`` function. ``range()`` is an inbuilt function in Python
-which can be used to generate a ``list`` of integers from a starting
-number to an ending number. Note that the ending number that you
-specify will not be included in the ``list``.
-
-.. #[Nishanth]: Show some examples of range without the step argument
- May be give an exercise with negative numbers as arguments
-
-{{{ switch to next slide, problem statement of the next problem in
-solved exercises }}}
-
-Now, let us print all the odd numbers from 1 to 50. Pause here and try
-to solve the problem yourself.
-
-Let us do it in our IPython interpreter for ease of use.
-
-{{{ switch focus to ipython interpreter }}}
-
-The problem can be solved by just using the ``range()`` function.
-
-It can be solved as,
-::
-
- print range(1,51,2)
-
-This time we passed three parameters to ``range()`` function unlike
-the previous case where we passed only two parameters. The first two
-parameters are the same in both the cases. The first parameter is the
-starting number of the sequence and the second parameter is the end of
-the range. Note that the sequence doesn't include the ending
-number. The third parameter is for stepping through the sequence. Here
-we gave two which means we are skipping every alternate element.
-
-{{{ switch to next slide, summary slide }}}
-
-Thus we come to the end of this tutorial. We learned about blocks in
-Python, indentation, blocks in IPython, for loop, iterating over a
-list and then the ``range()`` function.
-
-.. #[Amit]: There does seem to too much overhead of details. Should
- the first example be done using script is it necessary.
- Do add some things in evolutionary manner. Like introducing
- range as a list and doing a very very simple for loop.Like
- iterating over [1,2,3] .Before getting into a problem.
- And club details about problem in one paragraph and syntactic details
- in other.
-
-{{{ switch to next slide, thank you slide }}}
-
-Thank you!