Back-End Programming Exam > Back-End Programming Videos > Perl Building Blocks: An Introduction to Perl > Perl Tutorial - 16: Check Element Existence
Perl Tutorial - 16: Check Element Existence Video Lecture | Perl Building Blocks: An Introduction to Perl - Back-End Programming
FAQs on Perl Tutorial - 16: Check Element Existence Video Lecture - Perl Building Blocks: An Introduction to Perl - Back-End Programming
| 1. What is the purpose of checking element existence in Perl programming? |  |
Ans. Checking element existence is important in Perl programming to ensure that the program runs smoothly and avoids any errors or unexpected behavior. By checking the existence of elements, we can handle situations where the element may not be present and take appropriate actions accordingly.
| 2. How can we check if an element exists in Perl? | |
Ans. In Perl, we can check the existence of an element using the "exists" keyword. We can use it with the hash data structure to check if a specific key exists or with an array to check if a specific index exists. The "exists" keyword returns true if the element exists, and false otherwise.
| 3. Can we check for the existence of multiple elements in Perl? | |
Ans. Yes, in Perl, we can check for the existence of multiple elements using the "exists" keyword in a loop. For example, we can iterate over an array of elements and check if each element exists in a hash using the "exists" keyword. This allows us to perform different actions based on the presence or absence of multiple elements.
| 4. What happens if we try to access a non-existent element in Perl? | |
Ans. If we try to access a non-existent element in Perl, it will not raise an error or exception. Instead, Perl will return an undefined value. It is important to handle such cases properly in our code to avoid any unexpected behavior or errors.
| 5. Are there any alternatives to the "exists" keyword for checking element existence in Perl? | |
Ans. Yes, there is an alternative to the "exists" keyword in Perl, which is the "defined" keyword. While "exists" checks if the key or index exists, "defined" checks if the value associated with the key or index is defined or not. Both keywords serve different purposes, and the choice depends on the specific requirement of the program.
Text Transcript from Video
hello guys welcome to my channel this is
the 16th tutorial in this course and in
this tutorial we're going to talk about
the exists subroutine or the exist
function in Perl and we're gonna see how
we can use that function to determine if
a particular key value pair exists in a
Perl hash or not so as you guys can see
I've got a file opened up here it's
called hashes underscore existing start
PL and this file on line number 3 I have
created a hash called tennis and I'm
sure you guys are familiar with the
structure of this particular hash by now
we've used it in multiple tutorials and
in this hash I've got the ranks of
tennis players as keys and their
corresponding names as values so Novak
has one roger has two and he has three
and K has four now you see lot of code
from line number four to line number
eleven and you know I'm using the
if/else construct in this tutorial and
we are going to discuss the if/else
construct and you know some other
decision statements in future tutorials
in this course but for the time being I
don't want you to worry about the syntax
of F else I just want you to understand
what the exists function can do for you
so the exists function can tell you
whether there is information about a
particular key in a hash or not and it's
very simple to use you just type exists
and then within parenthesis you type the
name of your hash with a dollar symbol
because you're making a scalar check and
then within curly braces you type the
key for which you are making your search
so you know let's say we want to know if
there is information about rank for in
this hash tennis so you know in that
case I would have to put 4 within curly
braces here and the if else construct
here is just going to help me print you
know some text if the value for rank 4
exists in the hash then I'm going to
print rank 4 belongs to and I'm going to
show the name of the player to which the
rank belongs and if there is no
information about the player who holds
the rank 4 then
I'm going to display the text oops we
don't have the requested information
right so that's what the script is going
to do the file is saved let me run it so
at the moment we have the key for in the
hash and you know the corresponding name
is K so you can see that rank four
belongs to K and what I'll do is I'll
delete this from the hash save the file
and run the script again and now we see
that oops we don't have the requested
information so that is what the exist
function can do and as I mentioned
earlier we're going to talk about the F
else construct in a future tutorial so
that's it for the time being I hope you
guys had fun watching this video you may
subscribe to my channel if you haven't
already I'm going to see you soon till
then take care
the 16th tutorial in this course and in
this tutorial we're going to talk about
the exists subroutine or the exist
function in Perl and we're gonna see how
we can use that function to determine if
a particular key value pair exists in a
Perl hash or not so as you guys can see
I've got a file opened up here it's
called hashes underscore existing start
PL and this file on line number 3 I have
created a hash called tennis and I'm
sure you guys are familiar with the
structure of this particular hash by now
we've used it in multiple tutorials and
in this hash I've got the ranks of
tennis players as keys and their
corresponding names as values so Novak
has one roger has two and he has three
and K has four now you see lot of code
from line number four to line number
eleven and you know I'm using the
if/else construct in this tutorial and
we are going to discuss the if/else
construct and you know some other
decision statements in future tutorials
in this course but for the time being I
don't want you to worry about the syntax
of F else I just want you to understand
what the exists function can do for you
so the exists function can tell you
whether there is information about a
particular key in a hash or not and it's
very simple to use you just type exists
and then within parenthesis you type the
name of your hash with a dollar symbol
because you're making a scalar check and
then within curly braces you type the
key for which you are making your search
so you know let's say we want to know if
there is information about rank for in
this hash tennis so you know in that
case I would have to put 4 within curly
braces here and the if else construct
here is just going to help me print you
know some text if the value for rank 4
exists in the hash then I'm going to
print rank 4 belongs to and I'm going to
show the name of the player to which the
rank belongs and if there is no
information about the player who holds
the rank 4 then
I'm going to display the text oops we
don't have the requested information
right so that's what the script is going
to do the file is saved let me run it so
at the moment we have the key for in the
hash and you know the corresponding name
is K so you can see that rank four
belongs to K and what I'll do is I'll
delete this from the hash save the file
and run the script again and now we see
that oops we don't have the requested
information so that is what the exist
function can do and as I mentioned
earlier we're going to talk about the F
else construct in a future tutorial so
that's it for the time being I hope you
guys had fun watching this video you may
subscribe to my channel if you haven't
already I'm going to see you soon till
then take care
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Dec 23, 2024 Last updated |
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