Pratik kamble: Created page with "{| border=1 | '''Time''' | '''Narration''' |- | 00:01 | Welcome to the spoken tutorial on '''Dictionaries'''. |- | 00:05 |In this tutorial, we will learn to, Create '''dic..."

2019-06-11T08:37:22Z

Created page with "{| border=1 | '''Time''' | '''Narration''' |- | 00:01 | Welcome to the spoken tutorial on '''Dictionaries'''. |- | 00:05 |In this tutorial, we will learn to, Create '''dic..."

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{| border=1
| '''Time'''
| '''Narration'''

|-
| 00:01
| Welcome to the spoken tutorial on '''Dictionaries'''.

|-
| 00:05
|In this tutorial, we will learn to,

Create '''dictionaries'''

Add and delete '''data''' from '''dictionaries'''

Retrieve '''data''' from '''dictionaries'''

Check for presence of '''keys''' and

'''Iterate''' over elements.

|-
| 00:25
|To record this tutorial, I am using

'''Ubuntu Linux 16.04''' operating system

'''Python 3.4.3 '''and

'''IPython 5.1.0'''

|-
| 00:40
|To practise this tutorial, you should know how to

use''' basic data types '''and''' operators'''

If not, see the relevant '''Python''' tutorials on this website.

|-
| 00:54
| First we will learn about '''dictionaries'''.

|-
|00:58
|'''Dictionary''' is an unordered collection of items which has '''key:value''' pairs.

'''Dictionary''' is used to look up for a specific '''key''' and retrieve the corresponding '''value'''.

|-
| 01:12
| '''Keys''' are unique within a dictionary while '''values''' may not be.

|-
|01:18
|The values of a dictionary can be of any data type.

|-
|01:23
|But the keys must be of immutable data type such as '''strings''', '''numbers''' or '''tuples'''.

|-
| 01:31
| Let us start '''ipython'''. Open the '''terminal.'''

|-
| 01:37
| Type '''ipython3 '''and press '''Enter.''' From here onwards, remember to press the '''Enter''' key after typing every command on the '''terminal'''.

|-
| 01:50
| Let us start by creating an empty '''dictionary'''.

|-
|01:54
|Type, '''empty '''''is equal to''''' '''''open and close curly braces'' Note that unlike '''lists''', '''curly''' '''braces''' are used to define a '''dictionary'''.

|-
| 02:06
| Now let us see how to create a non empty '''dictionary'''.

|-
| 02:11
|Type as shown. Note that,

Each '''key:value pair''' is separated by a '''comma''',

Each '''key''' is separated from its value by a colon, and

The whole thing is enclosed in curly braces.

|-
| 02:29
| Here, we have defined four entries in the '''dictionary''' '''student'''. The '''keys''' are '''name, age, gender, class.'''

|-
| 02:44
| Type, '''student''' to see its content.

|-
| 02:50
| Next let us learn to access the dictionary elements.

|-
| 02:55
| The value of a '''dictionary''' can be accessed using the corresponding''' key'''.

|-
|03:01
|The '''syntax '''is: '''dictionary '''''underscore '''''name '''''inside square brackets '''''key'''

|-
| 03:07
| Now let us access the value for the key''' ‘name’.'''

|-
| 03:12
|Type, '''print''' ''inside brackets '''''student '''''inside square brackets inside single quotes '''''name'''

|-
| 03:21
|As expected it''' '''printed the output as''' raj.'''

|-
| 03:26
| Now we will retrieve the value for the key''' ‘class’'''

|-
| 03:31
|Type, '''print''' ''inside brackets '''''student '''''inside square brackets inside single quotes '''''class'''
It displays the output as 10.

|-
| 03:43
| If we try to access a '''value''' with a wrong '''key''', we get an error.

|-
| 03:49
|Type, '''student '''''inside square brackets inside single quotes '''''height'''

|-
| 03:56
|The '''interpreter''' gave us the '''KeyError:''' ''''height'''' This is because, '''key 'height' '''is not present in the '''student dictionary.'''

|-
| 04:05
|This is about creating '''dictionaries.'''

|-
| 04:09
| Next, let us see how to '''add''' or '''delete''' '''items '''in a '''dictionary'''.

|-
| 04:15
|First let us '''add''' an element''' height '''to the '''dictionary''' '''student.'''

Type, '''student '''''inside square brackets inside single quotes '''''height '''''is equal to''''' 6.2'''

|-
| 04:29
| Let us now check the content of the '''dictionary.'''

Type, '''student''' You can see that '''key-value''' ''''height': 6.2 '''is added to the '''dictionary student.'''

|-
| 04:42
| Next let us modify the '''element class '''of the '''dictionary''' '''student.'''

Type, '''student '''''inside square brackets inside single quotes '''''class '''''is equal to '''''11'''

|-
| 04:56
| Now, to check the content of the dictionary, type, '''student'''

|-
| 05:02
|As you can see, the value for '''class''' '''key''' is changed to '''11 .'''

|-
| 05:06
| Next let us learn to delete '''age '''from the '''dictionary''' '''student.'''

Type, '''del student '''''inside square brackets inside single quotes '''''age'''

|-
| 05:20
| Type, '''student''' You can see that now '''key-value''' ''''age': 16''' is deleted from '''student. '''

|-
| 05:29
| Next let us see how to check whether a '''key''' is present in a '''dictionary'''.

For that we can use the '''method in.'''

|-
| 05:39
| The method''' in''' will return '''True''' if the key is found in the '''dictionary.''' It will return '''False''' if '''key''' is not present.

|-
| 05:48
|Note that we can check only for the presence of the '''keys''' in '''dictionaries''' and not values.

|-
| 05:55
|'''Keys '''of a '''dictionary '''are not ordered. Hence, '''slicing''' and '''striding''' are not valid on '''dictionaries'''.

|-
| 06:03
| Let us try it with an example.

|-
| 06:06
|Type, ''inside single quotes '''''school in student''' We get '''False, '''since the '''key 'school' '''is not present in '''student.'''

|-
| 06:17
| Type, ''inside single quotes '''''name in student''' We get '''True''', as expected.

|-
| 06:25
|Next let us see how to retrieve keys and values of a dictionary.

Method '''keys'''() is used for getting a '''list''' of '''keys'''

Method''' values() '''is''' '''used''' '''for getting a '''list''' of '''values'''.

|-
| 06:40
| Now let us try the above methods with examples. Type, '''student''''' dot '''''keys '''''open and close brackets '' It returns the '''list''' of '''keys''' of the '''dictionary''' '''student.'''

|-
| 06:56
| Type, '''student '''''dot '''''values '''''open and close brackets ''
It returns the '''list''' of '''values''' of the '''dictionary''' '''student.'''

|-
| 07:07
| Next let us see the '''items method.'''

Type, '''student '''''dot '''''items '''''open and close brackets''

|-
| 07:16
|It returns a '''list''' of '''tuples''' of '''key-value pairs''' of the '''dictionary student.'''

|-
| 07:22
|The order of items of the list returned by''' keys(), values() '''and''' items()''' cannot be predicted.

|-
| 07:30
|In '''dictionaries, '''they are not in the order in which we inserted them.

|-
| 07:35
| Pause the video. Try this exercise and then resume the video.

|-
|07:41
| Print the '''keys''' and '''values''' of the '''dictionary student''' one by one. Hint: use the '''method''' '''items''' and '''for loop.'''

|-
| 07:50
| Switch back to the terminal for the solution.

|-
| 07:54
| Type as shown. It displays the keys and values one by one.

|-
| 08:02
| This brings us to the end of this tutorial. Let us summarize.

|-
| 08:08
|In this tutorial, we have learnt to,

Create '''dictionaries'''

Access '''elements''' of a '''dictionary''' using '''keys'''

Add '''elements''' to a '''dictionary''' by assigning a '''value''' to a '''key'''

|-
| 08:22
|Delete '''elements''' from a '''dictionary''' by using the '''function''' '''del'''

Retrieve the '''keys''' and '''values''' by using the '''methods''' '''keys'''() and '''values() '''respectively

|-
| 08:34
| and Iterate over '''elements''' of a '''dictionary''' using a '''for loop'''.

|-
| 08:39
| Here are some self assessment questions for you to solve

'''Dictionary d '''is defined as shown:

How do you retrieve the '''value 'b'?'''

Delete '''value 'b' '''from the '''dictionary d'''

|-
| 08:55
|And the answers,

'''d '''''inside square brackets''''' 2 '''gives the '''value 'b''''

'''del d '''''inside square brackets '''''2 '''deletes the '''value ‘b’'''

|-
| 09:10
| Please post your timed queries in this forum.

|-
| 09:14
| Please post your general queries on Python in this forum.

|-
| 09:19
| FOSSEE team coordinates the TBC project.

|-
| 09:23
| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India. For more details, visit this website.

|-
| 09:34
| This is Priya from IIT Bombay, signing off. Thanks for watching.

|}

Python-3.4.3/C3/Dictionaries/English-timed - Revision history

Pratik kamble: Created page with "{| border=1 | '''Time''' | '''Narration''' |- | 00:01 | Welcome to the spoken tutorial on '''Dictionaries'''. |- | 00:05 |In this tutorial, we will learn to, Create '''dic..."