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 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.
1 )
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 wildcard matches
more than one character in a string.
0:00
While we've been using character sets
to match one than one character,
0:05
there are shorter ways to
match some of these cases.
0:09
For example, instead of using 0 through
0:12
9 to match any numeral, use the \d.
0:17
The backslash is found often
in regular expressions, but
0:22
its meaning can differ,
according to where it's used.
0:25
Usually it's a way to say that
the character that follows has a special
0:29
meaning.
0:33
In this case,
it means that the d Isn't the letter d,
0:33
but a special instruction
to match a numeral.
0:38
And even though there are two
characters there, a backslash and
0:43
a d, the parser treats this
as a single character.
0:48
To match all alphanumeric characters
as well as an underscore, use \w.
0:52
This can be handy for
matching what's known as word characters.
1:00
The reason underscore is included is
that it's often used to space words
1:05
out that can't actually have
a space character in them.
1:10
For example, some file systems won't
let you use spaces in file names,
1:13
so it's become common practice
to use underscores instead.
1:19
To match whitespace characters,
you can use \s.
1:23
In addition to the space,
this wildcard includes other kinds
1:28
of whitespace, a tab and
a few kinds of line returns.
1:33
If you want to know more about
these special characters,
1:37
check the Teacher's Notes.
1:40
But for now, just think of the \s
as a way to match whitespace,
1:41
such as spaces, tabs, and new lines.
1:47
Also, the period or
dot matches any character.
1:50
Let's try some of these out.
1:55
Let's use a digit character shorthand
in place of the first set, \d.
1:58
Now any digit will be matched, but
we lost the match we had for the letter a.
2:06
We could match that by using
a word shorthand, like this.
2:12
Now any letter or digit will match.
2:18
I'll change this first line to use
a capital A, and it still matches.
2:22
Note that an underscore will also match.
2:28
Often when you're composing regex, you'll
want to control what you include though.
2:33
While the shorthand will often work,
you might find yourself going with
2:39
something more limiting,
like we had before.
2:43
We'll use \da, but
we'll put these in a character set.
2:48
Now the top string is no longer
matched because it's an underscore.
2:55
But if I change it back to an a,
the first two lines are matched.
2:59
I'll replace this space with a \s.
3:03
Now notice, if I add an 8 and
then a space,
3:08
and then change the second space to a tab,
3:13
the string still matches.
3:18
I'll add a 3 to the next line, And
3:21
instead of a space,
I'll create a new line by typing Enter.
3:26
See how the color carries over?
3:31
So these two lines are one match now.
3:33
Let's use the dot.
3:36
I'll replace the s with a dot.
3:38
All the same matches are still
there because the dot will
3:43
match any character at all.
3:46
Let's change one of these s's to be
an exclamation point, for example.
3:48
It's a match, or maybe a dollar sign.
3:56
As you can see,
the dot is a powerful character in regex.
4:00
You'll see it used in a lot
of examples around the web.
4:04
Remember that the question mark
matches zero or one character.
4:07
In other words, the character is optional.
4:12
I'll show you another example where
you might use this in a new tab.
4:16
You could use the question mark
to match both the American and
4:23
the British spellings of the word,
like color.
4:27
Check the notes for
some additional practice.
4:41
In the next video, I'll show you
how to match repeating characters.
4:44
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