--- a/dictionaries.rst Sat Oct 09 02:59:42 2010 +0530
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,177 +0,0 @@
-.. 8.4 LO: dictionaries (2)
-.. ------------------------
-.. * empty
-.. * filled
-.. * accessing via keys
-.. * .values(), .keys()
-.. * in
-.. * iteration
-
-============
-Dictionaries
-============
-
-{{{ show the welcome slide }}}
-
-Welcome to the spoken tutorial on dictionaries.
-
-{{{ switch to next slide, outline slide }}}
-
-In this tutorial, we will see how to create empty dictionaries, learn
-about keys and values of dictionaries. Checking for elements and
-iterating over elements.
-
-{{{ switch to next slide on overview of dictionaries }}}
-
-A dictionary in general, is designed to look up meanings of
-words. Similarly, Python dictionary is also designed to look up for a
-specific key and retrieve the corresponding value. Dictionaries are
-data structures that provide key-value mappings. Dictionaries are
-similar to lists except that instead of the values having integer
-indexes, dictionaries have keys or strings as indexes.
-
-Before we can proceed, start your IPython interpreter with the
-``-pylab`` option.
-
-{{{ start ipython interpreter by issuing command ipython -pylab }}}
-
-Let us start by creating an empty dictionary, type the following in
-your IPython interpreter.
-::
-
- mt_dict = {}
-
-Notice that unlike lists curly braces are used define ``dictionary``,
-
-{{{ move the mouse over curly braces to grab attention }}}
-
-Now let us see how to create a filled dictionary,
-::
-
- extensions = {'jpg' : 'JPEG Image', 'py' : 'Python script', 'html' : 'Html document', 'pdf' : 'Portable Document Format'}
-
-Notice that each key-value pair is separated by a comma
-
-{{{ move the mouse over the commas to grab attention }}}
-
-and each key and value are separated using a colon.
-
-{{{ move the mouse over the colon one by one to grab attention }}}
-
-Here, we defined four entries in the dictionary extensions. The keys
-are
-
-{{{ spell the keys letter by letter }}}
-
-jpg, py, html, and pdf.
-
-Simply type,
-::
-
- extensions
-
-in the interpreter to see the content of the dictionary. Notice that
-in dictionaries the order cannot be predicted and you can see that the
-values are not in the order that we entered in.
-
-Like in lists, the elements in a dictionary can be accessed using the
-index, here the index is the key. Try,
-::
-
- print extensions['jpg']
-
-It printed JPEG Image. And now try,
-::
-
- print extensions['zip']
-
-Well it gave us an error, saying that the key 'zip' is not in the
-dictionary.
-
-Pause here for some time and try few more keys. Also try jpg in
-capital letters.
-
-{{{ switch to next slide, adding and deleting keys and values in
-dictionaries }}}
-
-Well that was about creating dictionaries, now how do we add or delete
-items. We can add new items into dictionaries as,
-::
-
- extensions['cpp'] = 'C++ code'
-
-and delete items using the ``del`` keyword as,
-::
-
- del extension['pdf']
-
-Let us check the content of the dictionary now,
-::
-
- extensions
-
-So the changes have been made. Now let us try one more thing,
-::
-
- extensions['cpp'] = 'C++ source code'
- extensions
-
-As you can see, it did not add a new thing nor gave an error, but it
-simply replaces the existing value with the new one.
-
-Now let us learn how to check if a particular key is present in the
-dictionary. For that we can use ``in``,
-::
-
- 'py' in extensions
- 'odt' in extensions
-
-So in short it will return ``True`` if the key is found in the
-dictionary, and will return ``False`` if key is not present. Note that
-we can check only for container-ship of keys in dictionaries and not
-values.
-
-{{{ switch to next slide, Retrieve keys and values }}}
-
-Now let us see how to retrieve the keys and values. We can use the
-method ``keys()`` for getting a list of the keys in a particular
-dictionary and the method ``values()`` for getting a list of
-values. Let us try them,
-::
-
- extensions.keys()
-
-It returned the ``list`` of keys in the dictionary extensions. And now
-the other one,
-::
-
- extensions.values()
-
-It returned the ``list`` of values in the dictionary.
-
-{{{ switch to next slide, problem statement for the next solved
-exercise }}}
-
-Now let us try to print the data in the dictionary. We can use ``for``
-loop to iterate.
-::
-
- for each in extensions.keys():
- print each, "-->", extensions[each]
-
-
-{{{ switch to next slide, recap }}}
-
-This brings us to the end of this tutorial, we learned dictionaries
-and saw how to create an empty dictionary, build a dictionary with
-some data in it, adding data, ``keys()`` and ``values()`` methods, and
-iterating over the dictionaries.
-
-{{{ switch to next slide, thank you slide }}}
-
-Thank you!
-
-.. Author: Anoop Jacob Thomas <anoop@fossee.in>
- Reviewer 1:
- Reviewer 2:
- External reviewer: