Back-End Programming Exam > Back-End Programming Videos > Perl Building Blocks: An Introduction to Perl > Perl Tutorial - 18: Adding & Removing Hash Elements
Perl Tutorial - 18: Adding & Removing Hash Elements Video Lecture | Perl Building Blocks: An Introduction to Perl - Back-End Programming
FAQs on Perl Tutorial - 18: Adding & Removing Hash Elements Video Lecture - Perl Building Blocks: An Introduction to Perl - Back-End Programming
| 1. What is the syntax for adding a new element to a hash in Perl? |  |
Ans. To add a new element to a hash in Perl, you can use the following syntax:
```
$hash_name{key} = value;
```
For example, to add a new element with the key "name" and the value "John" to a hash named %person, you would write:
```
$person{name} = "John";
```
| 2. How can I check if a specific key exists in a Perl hash? | |
Ans. You can check if a specific key exists in a Perl hash by using the `exists` function. The syntax is as follows:
```
if (exists $hash_name{key}) {
# Key exists in the hash
# Perform desired actions
}
```
For example, to check if the key "age" exists in the %person hash, you would write:
```
if (exists $person{age}) {
print "The key 'age' exists in the hash.";
} else {
print "The key 'age' does not exist in the hash.";
}
```
| 3. How can I remove a specific key-value pair from a Perl hash? | |
Ans. To remove a specific key-value pair from a Perl hash, you can use the `delete` function. The syntax is as follows:
```
delete $hash_name{key};
```
For example, to remove the key-value pair with the key "name" from the %person hash, you would write:
```
delete $person{name};
```
| 4. Is it possible to remove all elements from a Perl hash at once? | |
Ans. Yes, it is possible to remove all elements from a Perl hash at once. You can do this by assigning an empty hash to the original hash variable.
For example, to remove all elements from the %person hash, you would write:
```
%person = ();
```
After this assignment, the %person hash will be empty.
| 5. Can I add multiple key-value pairs to a Perl hash at once? | |
Ans. Yes, you can add multiple key-value pairs to a Perl hash at once by using the curly brackets and the `=>` operator. The syntax is as follows:
```
%hash_name = (key1 => value1, key2 => value2, key3 => value3);
```
For example, to add three key-value pairs to the %person hash, you would write:
```
%person = (name => "John", age => 30, city => "New York");
```
This will add the key-value pairs "name" => "John", "age" => 30, and "city" => "New York" to the %person hash.
Text Transcript from Video
hello guys welcome to my channel this is
the eighteenth video in this course and
in this tutorial we're going to see how
we can add or remove key value pairs
from an existing hash in Perl so I've
got a script that's ready it's called
hashes underscore add remove and in this
script on line number three I have the
tennis hash with which we've been
working since eternity now and it's got
four keys and four values and the first
thing that we're going to do is we're
going to obtain the keys in this hash
and we're going to store the keys in an
array variable called my underscore
error so I'm doing that on line number
five I have created an array variable
called my underscore a Arad with the
other eight symbol and then I've used
the keys method to obtain or fetch the
keys in this hash tennis and you know
it's very simple we use the keys keyword
give a space and put % and then the name
of the hash and then I'm going to store
the size of this particular array
variable or basically the number of keys
in this hash in a variable called size
and then on line number seven I have a
print statement that is going to display
the orange size of the original hash I
should say and you know that is stored
in the scalar variable size so I have a
print statement on line number seven to
do that and now let's say you want to
add a key value pair to the sash you
want to add information about you know
rank five and let's say rank five
belongs to Tomas Berdych so you do that
by putting a dollar symbol because
you're making a scalar addition to this
hash so you put the dollar symbol the
name of the hash which is tennis and
then within curly braces you type the
the key for which you want to make an
addition so you want to add information
about rank 5 so you put 5 here and then
you put the equal to symbol and then you
know if it's a string value then within
double quotes you just type in that
value so in our case it would be board H
within quotes and a semicolon to
terminate the statement and this should
add voltage at rank 5 in this tennis
hash
so to confirm whether the addition has
happened you know normally or not we're
going to again fetch the size of this
hash using the same you know two
statements that we used here I'm again
using the keys system routine to you
know get the keys in the array variable
my underscore ARR and then I'm using the
scalar variable size to store the size
of the list and then I'm using the print
statement to display the value in this
variable after the addition so you know
here it should so forth and here it
should show five because I've just added
a key value pair now let's say you want
to delete a key value pair so you want
to delete the the key that you've just
inserted in the hash so that is very
simple you use the delete keyword so on
line number 15 I have just type delete a
given space and then since we are moving
removing you know a scalar value from
the hash you type the dollar symbol the
name of the hash which is tennis and
then within curly braces you type the
key for which you want to remove the
value so you know that would be five in
our case and again I have the same you
know set of statements similar set of
statements to display or pain the size
of the hash first and then displayed on
screen to confirm whether the deletion
has deletion has happened successfully
or not so I'll make sure that this file
is saved and I'll press f5 to execute
this and there we go we see that the
size of the hash initially is four and
then we did that addition thing and the
size of the hash after addition is 5 and
then we use a delete statement to remove
the key value pair that was added to the
hash and we see then that the size of
the hash after deletion well actually it
should be deletion here I have never in
my print statement on line number 19
we'll go back to that is false so I hope
you guys now understand how you can add
or remove key value pairs and you know
let me point out to the error that I
have on line number 19 it should be
deletion here instead of addition so
that's it for this tutorial I hope you
guys had fun and you may subscribe to my
channel if you
the eighteenth video in this course and
in this tutorial we're going to see how
we can add or remove key value pairs
from an existing hash in Perl so I've
got a script that's ready it's called
hashes underscore add remove and in this
script on line number three I have the
tennis hash with which we've been
working since eternity now and it's got
four keys and four values and the first
thing that we're going to do is we're
going to obtain the keys in this hash
and we're going to store the keys in an
array variable called my underscore
error so I'm doing that on line number
five I have created an array variable
called my underscore a Arad with the
other eight symbol and then I've used
the keys method to obtain or fetch the
keys in this hash tennis and you know
it's very simple we use the keys keyword
give a space and put % and then the name
of the hash and then I'm going to store
the size of this particular array
variable or basically the number of keys
in this hash in a variable called size
and then on line number seven I have a
print statement that is going to display
the orange size of the original hash I
should say and you know that is stored
in the scalar variable size so I have a
print statement on line number seven to
do that and now let's say you want to
add a key value pair to the sash you
want to add information about you know
rank five and let's say rank five
belongs to Tomas Berdych so you do that
by putting a dollar symbol because
you're making a scalar addition to this
hash so you put the dollar symbol the
name of the hash which is tennis and
then within curly braces you type the
the key for which you want to make an
addition so you want to add information
about rank 5 so you put 5 here and then
you put the equal to symbol and then you
know if it's a string value then within
double quotes you just type in that
value so in our case it would be board H
within quotes and a semicolon to
terminate the statement and this should
add voltage at rank 5 in this tennis
hash
so to confirm whether the addition has
happened you know normally or not we're
going to again fetch the size of this
hash using the same you know two
statements that we used here I'm again
using the keys system routine to you
know get the keys in the array variable
my underscore ARR and then I'm using the
scalar variable size to store the size
of the list and then I'm using the print
statement to display the value in this
variable after the addition so you know
here it should so forth and here it
should show five because I've just added
a key value pair now let's say you want
to delete a key value pair so you want
to delete the the key that you've just
inserted in the hash so that is very
simple you use the delete keyword so on
line number 15 I have just type delete a
given space and then since we are moving
removing you know a scalar value from
the hash you type the dollar symbol the
name of the hash which is tennis and
then within curly braces you type the
key for which you want to remove the
value so you know that would be five in
our case and again I have the same you
know set of statements similar set of
statements to display or pain the size
of the hash first and then displayed on
screen to confirm whether the deletion
has deletion has happened successfully
or not so I'll make sure that this file
is saved and I'll press f5 to execute
this and there we go we see that the
size of the hash initially is four and
then we did that addition thing and the
size of the hash after addition is 5 and
then we use a delete statement to remove
the key value pair that was added to the
hash and we see then that the size of
the hash after deletion well actually it
should be deletion here I have never in
my print statement on line number 19
we'll go back to that is false so I hope
you guys now understand how you can add
or remove key value pairs and you know
let me point out to the error that I
have on line number 19 it should be
deletion here instead of addition so
that's it for this tutorial I hope you
guys had fun and you may subscribe to my
channel if you
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About this Video
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Nov 22, 2024 Last updated |
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