Difference between revisions of "PERL/C2/Hash-in-Perl/English-timed"
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− | |Welcome to the spoken tutorial on ''' Hash''' in '''PERL'''. | + | |Welcome to the spoken tutorial on '''Hash''' in '''PERL'''. |
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− | | Hope you enjoyed this PERL tutorial. | + | | Hope you enjoyed this '''PERL''' tutorial. |
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Revision as of 17:55, 24 May 2015
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 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'll 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. |
08:59 | 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. |