Ruby Programming Tutorial - 25 - Extracting Numbers and Character Classes

what is going on guys welcome to your
25th Ruby tutorial and in this lesson
I'm going to show you guys how to
extract numbers from strings and also
how to use something called character
classes which is actually one of the
more popular features whenever we talk
about regular expressions but anyways
let's go ahead and make a simple
variable and we'll name it tuna because
gotta love tuna and I'll just write
something like I have 45 warts and my
llama has 62 now this actually is true
but nonetheless that's not important for
this tutorial now what we can do is we
can use this variable called tuna which
is the sentence right here and we can
run methods on it like scan now again
like I said the first thing I want to do
is extract all the numbers from the
string for example 4562 I want to take
anything that's a number and pull it out
and let me just go ahead and print it on
the screen or something
so scan the first thing we want to do is
we want to scan for a regular expression
a pattern of numbers now the simple for
a digit or a number is based or its
backslash d now what this is going to do
is it's going to match any digit however
the problem is whenever we scan a string
Ruby isn't going to know the difference
between is this a 4/5 or is it 45 well
in order to do that we need to add
another symbol and that's the plus sign
the plus sign basically means match any
number of joining digits not only 4 and
then 5 since these are together it's
basically writing the same is backslash
D or backslash d backslash D is
basically taking any number of digits
together and scanning for them now after
this what this is going to do is it's
going to scan for all the digits in now
we just want to extract them into a
variable like I don't know Z first thing
I thought of and print it out on the
screen so you guys already know what
this does so now let's go ahead and see
what we got 45 and 62 so basically it
doesn't matter
I said I have four warts I have 6821
warts as long as it is any digit any
number of digits long any length it will
extract it and that's what the plus sign
does in the plus sign by the way it
doesn't only work with numerical digits
but you can use this in a wide variety
of regular expressions and we'll
probably look at that a little bit later
on but for now we got something else to
cover and that is called character
classes now character classes is just
basically a fancy term for group now
what we can do is instead of scanning
for maybe the letter A or maybe the
letter F or maybe the number nine we can
group all of these things together and
scan for anything inside this group so
now let me go ahead and write a string
like wow I freaking love beans
explanation point why the heck not and
now what we want to do is we want to
scan but we just don't want to scan for
any single thing we want to scan for a
group so anytime you're making a group
you surround it in square brackets now
inside your square brackets write
everything that you want to be in that
group so basically let's go ahead and
scan for the letters a I'm just going to
pick like s and W a s W they're just
like the first three ones I saw so
basically any time we come across the
letters a s or W let's just go ahead and
keep it simple printing out on the
screen so extract those values storm and
variable called Y and print Y out on the
screen so check it out remember our
initial string was wow I freaking love
beans by the way I don't I hate beans so
anyways what it did is it put out W waa
s why is that because in our group was
the letters a s and W so first they came
across the W then it came across another
W then it came across this a right here
then it came across this a right here
and last but not least it came across
this s so anything that was in our group
and we told it was a group by
surrounding it was
we're brackets it extracted imprinted
data on the screen now aside from that
we can also have a group of characters
so instead of a s and W we can make or
did I just say instead of a s and W we
can have a group of characters I if I
did then I said that wrong what I meant
was instead of just having a bunch of
single items in our group we can
actually have a range of items so say
for example that we wanted to include
all the letters from A to G we can write
this ABCD efg okay but who the heck
wants to type that much not me so
anytime you want to work with a range of
letters from this just use the - a - G
now this is actually a pretty easy
symbol to understand because this is how
you would write it in plain English so
basically a - G is short for all the
lowercase letters A to G so instead of
just a s and W like before any times at
any time it comes across any letter A to
G it's going to extract it and print it
out on the screen so check it out first
it came across F e in I'm not going to
read all the letters to you but just
note that all of these letters that it
extracted are in the range of A to G
anything H and above H does come after G
right x eh yep got it right anything H
to Z is not included in this so there
you go that is how you make only well I
call them groups but they're technically
called character classes so if you're
writing this on a test or something or
writing on an essay make sure to call
them character classes and another thing
that is how you scan four digits
whenever you want to do something like
extract the digits from a string of text
so anyways like I said I know regular
expressions are kind of confusing at
first but I'm going to show you guys
probably one more tutorial using regular
expressions and it'll probably pound the
concept through so for now thank you
guys for watching I'm good subscribe and
I'll see you guys next time