Difference between revisions of "PERL/C2/Hash-in-Perl/English-timed"

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|* '''Ubuntu Linux 12.04''' operating system  
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|* '''Perl 5.14.2''' and  
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|* Adding key is- '''dollar hashName open curly bracket'''
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| Press ''' Ctrl+S''' to '''save''' the file.  
 
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| ''' perl hashKeyOperations dot pl'''  
 
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|'''keys''' function is used to retrieve all the keys of a  '''hash''',
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|'''keys()''' function is used to retrieve all the keys of a  '''hash''',
 
   
 
   
 
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| '''values''' function returns '''values''' of all the '''keys''' whereas  
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| ''''each'''' function iterates over ''' hash''' and returns '''key/value''' pair from ''' hash'''.  
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|'''keys''' function on  hash returns an array which contains all '''keys''' of '''hash.'''
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| '''values''' function on  hash returns an array of values for all '''keys''' of hash.
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|Let us summarize.  
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|Loop over '''hash''' using '''keys, values''' and '''each''' function.  
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|For more details, please write to contact at: spoken hyphen tutorial dot org
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Latest revision as of 15:49, 10 March 2017

Time Narration
00:01 Welcome to the spoken tutorial on Hash in PERL.
00:05 In this tutorial, we will learn about:
00:09 Hash in PERL and
00:11 accessing an element of a hash.
00:14 For this tutorial, I am using:
00:16 Ubuntu Linux 12.04 operating system
00:21 Perl 5.14.2 and
00:24 gedit Text Editor.
00:26 You can use any text editor of your choice.
00:30 To practice this tutorial, you should have knowledge of variables & data Structures in PERL.
00:38 Knowledge of comments, loops, conditional statements and arrays will be an added advantage.
00:46 Please go through the relevant spoken tutorials on the Spoken Tutorial website.
00:52 Hash is an unordered collection of data.
00:56 It's a key/value pair data structure.
00:59 Hash keys are unique.
01:01 However, Hash can have duplicate values.
01:05 This is the declaration of a hash.
01:08 Let us see how to get the value of a key from hash.
01:12 The syntax for accessing the value of a key is:
01:17 dollar hashName open curly bracket single quote keyName single quote close curly bracket.
01:26 Let us understand hash using a sample program.
01:31 I have already typed the code in perlHash dot pl file in gedit.
01:37 Type the code as shown in your perlHash dot pl file.
01:42 Hash in PERL is declared with percentage sign (%).
01:47 These are the keys of hash
01:49 and these are the values of hash.
01:53 Note: To access key of a hash, one has to use dollar sign.
01:59 Press Ctrl + S to save the file.
02:02 Then switch to terminal and execute the Perl script as:
02:08 perl perlHash dot pl
02:11 and press Enter.
02:14 The output is as shown on the terminal.
02:19 Now, let us see add and delete of keys from hash.
02:24 The syntax for:
02:26 Adding key is- dollar hashName open curly bracket
02:30 single quote KeyName single quote
02:34 close curly bracket equal to $value semicolon.
02:40 Deleting key is- delete dollar hashName open curly bracket
02:46 single quote KeyName single quote close curly bracket semicolon.
02:53 Now, let us understand this using a sample program.
02:58 I have already typed the code in hashKeyOperations dot pl file.
03:05 This is the declaration of a hash.
03:08 We will be adding, deleting the keys from this hash.
03:13 Here we are adding a key to an already created hash.
03:18 It is like assigning a value to a variable.
03:23 delete keyword is used to delete the key.
03:27 We need to pass the key to delete it.
03:31 Press Ctrl+S to save the file.
03:35 Switch to the terminal and execute the Perl script as:
03:40 perl hashKeyOperations dot pl
03:44 and press Enter.
03:47 Output will be as shown on the terminal.
03:52 Let us look at sorting of hash keys and values.
03:57 Syntax to sort keys is:
04:00 sort open bracket keys percentage hashName close bracket semicolon.
04:07 Similarly, we can sort hash values as:
04:11 sort open bracket values percentage hashName close bracket semicolon.
04:18 Let us understand sorting functionality using a sample program.
04:24 Let me switch to sortHash dot pl on gedit.
04:30 Type the code as displayed on the screen, in your sortHash dot pl file.
04:36 Here, we have declared hash of address.
04:41 Here, to sort the keys, we have used the sort inbuilt function along with the keys function.
04:49 This will sort the hash keys in alphabetical order.
04:54 Similarly, we can use the sort function on values of hash.
04:59 Sorting can also be done on numeric keys and/or values.
05:05 Save the file and switch to terminal.
05:09 Execute the script by typing perl sortHash dot pl and press Enter.
05:17 The output will be as shown on the terminal.
05:22 Now, let us see how to get all keys and values of a hash.
05:27 PERL provides inbuilt function to fetch all the hash keys and values.
05:34 keys() function is used to retrieve all the keys of a hash,
05:40 values() function returns values of all the keys whereas
05:46 each() function iterates over hash and returns key/value pair from hash.
05:53 Let us understand these using a sample program.
05:57 For this, we'll use perlHash dot pl script which we have created earlier in this tutorial.
06:07 Type the following piece of code as shown on the screen.
06:12 Let us understand the code now.
06:15 keys() function on hash returns an array which contains all keys of hash.
06:22 values() function on hash returns an array of values for all keys of hash.
06:30 each() function returns the key/value pair.
06:34 Here, we have used the while loop.
06:36 It will iterate over each key/value pair of hash that is returned by each function.
06:43 Press Ctrl+S to save the file.
06:48 Now, let us execute the script on the terminal by typing
06:53 'perl perlHash dot pl'
06:58 and press Enter.
07:01 The following output will be seen on the terminal.
07:05 Now, let us see few other ways of looping over hash.
07:10 We can use foreach loop to iterate over each key of hash.
07:15 Then perform a set of actions on the value of key.
07:20 The syntax is as displayed on the screen.
07:24 Here, each iteration of foreach loop will assign key from hash to $variable.
07:32 Then, it will use that $variable to fetch the value or to perform a set of actions.
07:40 Similarly, we can loop over hash values as shown on the screen.
07:47 We will look at sample program.
07:49 So, let me switch to loopingOverHash dot pl in gedit.
07:55 Type the following piece of code as shown in your loopingOverHash dot pl.
08:02 This piece of code returns single key of hash.
08:07 Here, in our case,
08:09 1st time dollar key ($key) contains the Department as key.
08:15 In the next iteration of foreach, Name key is returned.
08:21 Note: Hash is an unordered collection of data.
08:26 So, keys returned will not be in the sequence defined at the time of creating hash.
08:33 The loop on values works in a similar way.
08:38 Press Ctrl + S to save the file.
08:41 Then, switch to terminal and execute the Perl script as:
08:46 perl loopingOverHash dot pl
08:50 and press Enter.
08:53 The following output is displayed on the terminal.
08:58 Let us summarize. In this tutorial, we learnt:
09:01 Hash in PERL and
09:03 accessing elements of a hash
09:05 using sample programs.
09:08 Here is an assignment for you:
09:11 Declare hash having student name as key
09:15 and his/her percentage as the value.
09:18 Loop over hash using keys(), values() and each() function.
09:24 Then print the percentage of each student.
09:29 Watch the video available at the following link.
09:32 It summarizes the Spoken Tutorial project.
09:37 If you do not have good bandwidth, you can download and watch it.
09:42 The Spoken Tutorial Project team: Conducts workshops using spoken tutorials.
09:49 Gives certificates to those who pass an online test.
09:53 For more details, please write to: contact at spoken hyphen tutorial dot org.
10:02 Spoken Tutorial project is a part of the "Talk to a Teacher" project.
10:06 It is supported by the National Mission on Education through ICT, MHRD, Government of India.
10:15 More information on this mission is available at: spoken hyphen tutorial dot org slash NMEICT hyphen Intro.
10:26 Hope you enjoyed this PERL tutorial.
10:30 This is Amol, signing off.
10:33 Thanks for joining.

Contributors and Content Editors

Gaurav, Nancyvarkey, PoojaMoolya, Sandhya.np14

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