Heads up! To view this whole video, sign in with your Courses account or enroll in your free 7-day trial. Sign In Enroll
Preview
Start a free Courses trial
to watch this video
Learn some shortcut characters for some common character sets.
Practice
Copy both the Match and the Exclude set of test strings from each exercise below into a Regex tester like RegEx Pal or regex101. Using what you've learned so far, create a regular expression that will match all of the strings in the Match set and exclude the ones in the Exclude set.
Match:
7849
3472
8901
70502
23470
90496
Exclude:
abcde
ABCDE
2 )
Match:
1 a
2 a
3 a
4 a
5 a
8 a
9 b
Exclude:
4 c
4 E
3 )
Match:
8345 Gable
7238 Gable
2349 Table
8475 Cable
0994 Fable
1047 Zable
Exclude:
5633 gable
jklh 3able
4 )
Match:
bat
cat
data
eat
fast
12_6
Exclude:
$%#$@
Related Discussions
Have questions about this video? Start a discussion with the community and Treehouse staff.
Sign upRelated Discussions
Have questions about this video? Start a discussion with the community and Treehouse staff.
Sign up
A regular expression wild card matches
more than one character in a string.
0:00
While we've been using character sets
to match more than one character,
0:05
there are shorter ways
to match some cases.
0:08
For example, instead of using [0-9]
to match any numeral, use [SOUND] \d.
0:11
The backslash is found often
in regular expressions, but
0:18
its meaning can differ
according to where it's used.
0:21
Usually, it's a way to say that
the character that follows
0:24
has a special meaning.
0:27
In this case,
it means the d isn't the letter d, but
0:29
a special instruction to match a numeral.
0:33
Even though there are two
characters there, a backslash and
0:36
a d, the parser treats this
as a single character.
0:39
To match all alphanumeric characters,
as well as an underscore, use \w.
0:44
This can be handy for
matching what's known as word characters.
0:49
The reason the underscore is included
is that it's often used to space words
0:54
out that can't actually have
a space character in them.
0:58
For example, some file systems won't
let you use spaces in file names.
1:01
So it's become common to
use underscores instead.
1:06
[SOUND] To match white space characters,
[SOUND] you can use \s.
1:09
In addition to the space, this wild card
includes other kinds of white space,
1:14
a tab and
a few kinds of line return characters.
1:19
If you want to know more about
these special characters,
1:22
check out the teacher's notes,
but for now just think of \s as
1:25
a way to match white space,
such as spaces, tabs and new lines.
1:29
Also the period or
dot matches any character.
1:34
Let's try some of these out.
1:39
Let's use a digit character shorthand
in place of the character set
1:40
at the beginning.
1:44
Now any digit will be matched but
we lost the match we had of the letter A.
1:47
We could match that by using
a word shorthand like so.
1:52
Now any letter or digit will match.
1:56
I'll change the first line to
an uppercase A And it still matches.
1:59
Note an underscore will also match.
2:04
Often when you're composing reg xs, you'll
want to control what character you include
2:08
and while the word shorthand
will often work, you might
2:13
find yourself going with something
more limiting like what we had before.
2:16
We can include these shorthands
inside character sets.
2:21
If I create a character set
with a digit shorthand and
2:25
an a, the expression matches
the top two strings again.
2:28
I'll replace this space
character with a \s.
2:33
Now if I add an 8 and
a space to the next line, and
2:39
then replace this space with a tab,
the string still matches.
2:44
I'll add a 3 to the next line and
2:49
replace this space with a new
line character by pressing Enter.
2:52
See how the color carries over?
2:59
So these two lines are one match now.
3:01
Let's use the dot.
3:04
I'll replace the S with a dot.
3:06
All the same matches are still there,
3:09
because the dot will match
any character at all.
3:10
Let's change one of these Ss to be
an exclamation point, for example.
3:13
Or a dollar sign.
3:19
As you can see,
the dot is a powerful character in regexs.
3:21
You'll see it in a lot of
examples around the web.
3:25
Remember that the question mark
matches zero or one character.
3:28
In other words, the character is optional.
3:32
I'll show you another example of where
you might use this in the next tab.
3:35
You could use a question mark
to match both American and
3:39
British spellings of the word color,
like this.
3:42
Check the teacher's notes for
some additional practice.
3:45
In the next video, I'll show you
how to match repeating characters.
3:47
You need to sign up for Treehouse in order to download course files.
Sign upYou need to sign up for Treehouse in order to set up Workspace
Sign up