Python/C3/Dictionaries/English-timed

Time	Narration
00:01	Hello friends and Welcome to the spoken tutorial on 'dictionaries'.
00:05	At the end of this tutorial, you will be able to, Create dictionaries. Add and delete data from dictionaries. Retrieve data from dictionaries. Check for container-ship of keys. Iterating over elements.
00:20	Before beginning this tutorial,we would suggest you to complete the tutorial on "Basic datatypes and operators".
00:27	A dictionary in general, is designed to look up for meanings of words.
00:35	Similarly, Python dictionary is also designed to look up for a specific key and retrieve the corresponding value.
00:43	Dictionaries are data structures that provide key-value mappings.
00:47	Dictionaries are similar to lists except that instead of the values having integer indexes, dictionaries have keys or strings as indexes.
00:58	We start our ipython interpreter as, ipython
01:07	Let us start by creating an empty dictionary.
01:12	Type the following in your IPython interpreter,mt underscore dict = closing curly brackets
01:25	Notice that unlike lists, curly braces are used to define a dictionary
01:33	Now let us see how to create a non-empty dictionary,
01:37	so type extensions = open curly brackets in single quotes jpg colon 'JPEG Image' comma 'py' colon 'Python script' comma 'html' colon 'Html document' comma pdf colon Portable Document Format close curly brackets
02:08	Notice that each key-value pair is separated by a comma.
02:17	and each key value are separated using a colon.
02:23	Here, we have defined four entries in the dictionary extensions.
02:29	The keys are jpg comma py comma html comma and pdf.
02:36	Simply type,extensions in the interpreter to see the content of the dictionary.
02:40	So type extensions.
02:45	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.
02:53	Like lists, the elements in a dictionary can be accessed using the index, here the index is the key.
03:06	We type, print extensions in closing brackets in single quotes jpg.
03:25	NOW It printed JPEG Image. And now type print extensions within square brackets zip.
03:42	Well it gave us an error, saying that the key 'zip' is not in the dictionary.
03:48	So Pause here for some time and try few more keys.
03:52	Also try jpg in capital letters.
03:58	<continue from paused state Well that was about creating dictionaries, now how do we add or delete items?
04:09	We can add new items into dictionaries as,
04:13	Type extensions within square brackets in single quotes cpp is equal to in single quotes C++ then code.
04:36	and delete items using the del keyword as, type del space extensions and in square brackets and single quotes pdf.
04:51	Let us check the content of the dictionary now,
04:54	So type extensions.
04:57	So the changes have been made.
04:59	let us try one more thing, type extensions within square brackets and in single quotes cpp is equal to in single quote C++ and source code. then type again extensions.
05:21	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.
05:29	Now let us learn how to check if a particular key is present in the dictionary.
05:33	For that we can use the method in,
05:37	So type within single quotes py in extensions.
05:45	Then type odt in extensions.
05:53	It will return True if the key is found in the dictionary, and will return False if key is not present.
06:00	Note that we can check only for container-ship of keys in dictionaries and not values.
06:07	Now let us see how to retrieve the keys and values.
06:10	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.
06:20	Let us try them, type extensions dot key closing brackets.
06:31	It returned the list of keys in the dictionary extensions.
06:35	And now the other one is extensions dot values and closing brackets.
06:42	It returned the list of values in the dictionary.
06:45	Pause the video here, try out the following exercise and resume the video.
06:49	Print the keys and values in the dictionary one by one.
06:54	Now Switch to terminal for solution.
06:58	Type for each in extensions dot keys closing brackets colon then, print each comma within double quotes hyphen hyphen greater symbol, extensions and in square brackets each.
07:35	This brings us to the end of this tutorial.
07:39	In this tutorial, we have learn't to,
07:41	1. Create dictionaries namely -- - empty dictionaries - dictionaries with data.
07:45	2. Access elements in the dictionaries using the keys.
07:49	3. Add elements to a dictionary by assigning a key value.
07:55	4. Delete elements from a dictionary by using the function del
08:00	5. Retrieve the keys and values by using the methods .keys() and.values() respectively.
08:06	6. Iterate over elements of a dictionary using a for loop.
08:11	Here are some self assessment questions for you to solve
08:15	1. First one, Container-ship of values can be checked in a python dictionary - true or false.
08:22	2. Second one is, Consider the python dictionary x is equal to within curly brackets 'a' colon ['a','b','c'], 'b' colon (1, 2, 3), 1 colon then again another curly braces 1 colon 'one' comma 2 colon 'two' comma 10 colon within curly brackets 10 colon 'ten', 11 colon 'eleven' and close the curly brackets.
08:52	What will the following code return?
08:57	(1, 2, 3) in x.values(). True. False
09:05	Then container-ship of values cannot be checked in dictionaries
09:10	The dictionary is invalid
09:13	So Lets look at the answers,
09:16	1.The answer of first one, False.
09:19	Container-ship of only keys can be checked in a python dictionary.
09:27	2. Second one is, True
09:31	Hope you have enjoyed this tutorial and found it useful.
09:35	Thank you!

Contributors and Content Editors

Gaurav, Minal, PoojaMoolya, Sneha