Difference between revisions of "PERL/C2/Hash-in-Perl/English-timed"
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Revision as of 14:56, 16 June 2014
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| 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 Linux12.04 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 practise 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 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 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 a 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 hash. |
| 05.27 | Perl provides inbuilt function to fetch all the hash keys and values. |
| 05.34 | keys function is used to retrive all the keys of 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 a 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 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 summaries 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. |
