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diff --git a/dictionaries/script.rst b/dictionaries/script.rst index a8099c8..e272e07 100644 --- a/dictionaries/script.rst +++ b/dictionaries/script.rst @@ -4,9 +4,8 @@ .. At the end of this tutorial, you will be able to .. 1. Create dictionaries -.. #. Add data to dictionaries -.. #. Retrieve data -.. #. use ``.keys()`` and ``.values()`` methods +.. #. Add and delete data from dictionaries +.. #. Retrieve data from dictionaries .. #. Check for container-ship of keys .. #. Iterate over elements @@ -23,175 +22,343 @@ Language Reviewer : Bhanukiran Checklist OK? : <11-11-2010, Anand, OK> [2010-10-05] -.. #[Puneeth: Quickref] ============ Dictionaries ============ -{{{ show the welcome slide }}} +.. L1 -Welcome to the spoken tutorial on dictionaries. +{{{ Show the first slide containing title, name of the production +team along with the logo of MHRD }}} -{{{ switch to next slide, outline slide }}} +.. R1 -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. +Hello friends and Welcome to the spoken tutorial on 'dictionaries'. + +.. L2 + +{{{ switch to slide containing objectives }}} + +.. R2 + +At the end of this tutorial, you will be able to, + + 1. Create dictionaries. + #. Add and delete data from dictionaries. + #. Retrieve data from dictionaries. + #. Check for container-ship of keys. + #. Iterate over elements. + +.. L3 + +{{{ Switch to the pre-requisite slide }}} + +.. R3 + +Before beginning this tutorial,we would suggest you to complete the +tutorial on "Basic datatypes and operators". + +.. L4 {{{ switch to next slide on overview of dictionaries }}} -A dictionary in general, is designed to look up meanings of +.. R4 + +A dictionary in general, is designed to look up for 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. -We need ipython interpreter for this tutorial, start it by issuing the -command ``ipython`` in command line. +.. R5 + +We start our ipython interpreter as, -.. #[Puneeth: We don't need pylab] +.. L5 -{{{ start ipython interpreter by issuing command ipython }}} +{{{ Open the terminal }}} +:: -{{{ switch to next slide, Creating dictionary }}} + ipython -Let us start by creating an empty dictionary, type the following in +.. R6 + +Let us start by creating an empty dictionary. Type the following in your IPython interpreter. + +.. L6 :: mt_dict = {} -Notice that unlike lists, curly braces are used define ``dictionary``. +.. R7 -{{{ move the mouse over curly braces to grab attention }}} +Notice that unlike lists, curly braces are used to define a ``dictionary``. + +.. L7 + +{{{ move the mouse over curly braces }}} + +.. R8 Now let us see how to create a non-empty dictionary, + +.. L8 :: - extensions = {'jpg' : 'JPEG Image', 'py' : 'Python script', 'html' : 'Html document', 'pdf' : 'Portable Document Format'} + extensions = {'jpg' : 'JPEG Image', 'py' : 'Python script', + 'html' : 'Html document', 'pdf' : 'Portable Document Format'} + +.. R9 -Notice that each key-value pair is separated by a comma +Notice that each key-value pair is separated by a comma. -{{{ move the mouse over the commas to grab attention }}} +.. L9 + +{{{ move the mouse over the commas }}} + +.. R10 and each key and value are separated using a colon. -{{{ move the mouse over the colon one by one to grab attention }}} +.. L10 + +{{{ move the mouse over the colon one by one }}} -Here, we defined four entries in the dictionary extensions. The keys -are +.. R11 -{{{ spell the keys letter by letter }}} +Here, we have defined four entries in the dictionary extensions. +The keys are jpg, py, html, and pdf. -Simply type, +Simply type,extensions in the interpreter to see the content +of the dictionary. + +.. L11 :: 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. +.. R12 + +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. + +.. L12 {{{ switch to next slide, accessing elements }}} +.. R13 + Like in lists, the elements in a dictionary can be accessed using the -index, here the index is the key. Try, +index, here the index is the key. We type, + +.. L13 + +{{{ Switch to terminal }}} :: print extensions['jpg'] +.. R14 + It printed JPEG Image. And now try, + +.. L14 :: print extensions['zip'] +.. R15 + 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 }}} - +<continue from paused state> Well that was about creating dictionaries, now how do we add or delete items. We can add new items into dictionaries as, + +.. L15 :: extensions['cpp'] = 'C++ code' +.. R16 + and delete items using the ``del`` keyword as, + +.. L16 :: - del extension['pdf'] + del extensions['pdf'] + +.. R17 Let us check the content of the dictionary now, + +.. L17 :: extensions +.. R18 + So the changes have been made. Now let us try one more thing, + +.. L18 :: extensions['cpp'] = 'C++ source code' extensions +.. R19 + As you can see, it neither added a new thing nor gave an error, but it simply replaced 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``, +dictionary. For that we can use the method ``in``, + +.. L19 :: 'py' in extensions 'odt' in extensions +.. R20 + 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. +.. L20 + {{{ switch to next slide, Retrieve keys and values }}} +.. R21 + 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, +values. + +.. R22 + +Let us try them, + +.. L22 + +{{{ Switch to terminal }}} :: extensions.keys() +.. R23 + It returned the ``list`` of keys in the dictionary extensions. And now the other one, + +.. L23 :: extensions.values() +.. R24 + It returned the ``list`` of values in the dictionary. -{{{ switch to next slide, problem statement for the next solved -exercise }}} +Pause the video here, try out the following exercise and resume the video. + +.. L24 + +.. L25 + +{{{ Show slide with exercise 1 }}} + +.. R25 + + Print the keys and values in the dictionary one by one. + +.. R26 + +Switch to terminal for solution. -Now let us try to print the data in the dictionary. We can use ``for`` -loop to iterate. Pause here and try to do it yourself. +.. L26 -It can be solved as, +{{{continue from paused state}}} +{{{ Switch to the terminal }}} :: for each in extensions.keys(): print each, "-->", extensions[each] -{{{ switch to next slide, summary }}} +.. L27 + +{{{ Show summary slide }}} + +.. R27 + +This brings us to the end of this tutorial.In this tutorial, +we have learnt to, + + 1. Create dictionaries namely -- + - empty dictionaries + - dictionaries with data. + #. Access elements in the dictionaries using the keys. + #. Add elements to a dictionary by assigning a value to a key. + #. Delete elements from a dictionary by using the function ``del``. + #. Retrieve the keys and values by using the methods ``.keys()`` and + ``.values()`` respectively. + #. Iterate over elements of a dictionary using a ``for`` loop. + +.. L28 + +{{{Show self assessment questions slide}}} + +.. R28 + +Here are some self assessment questions for you to solve + + +1. Container-ship of values can be checked in a python dictionary + + - True + - False + +2. Consider the python dictionary ``x = {'a' : ['a','b','c'], 'b' : + (1, 2, 3), 1 : {1 : 'one', 2 : 'two'}, 10 : {10 : 'ten', 11 : + 'eleven'}}``. What will the following code return? + ``(1, 2, 3) in x.values()``. + + - True + - False + - Container-ship of values cannot be checked in dictionaries + - The dictionary is invalid + +.. L29 + +{{{solution of self assessment questions on slide}}} + +.. R29 + +And the answers, + +1. False.Container-ship of only keys can be checked in a python + dictionary. + +2. True + +.. L30 -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 thank you slide }}} -{{{ switch to next slide, thank you slide }}} +.. R30 +Hope you have enjoyed this tutorial and found it useful. Thank you! |