Character Sets
2 min read ·
Character sets allow you to match one character from a group of characters using square brackets.
Using []
Square brackets are used to define a set of characters.
Matches:
- cat
- bat
- rat
Ranges a to z
You can define a range of characters.
This matches lowercase words.
Multiple Ranges
Matching Digits
Negation
Use ^ inside brackets to match everything except given characters.
Matches all non digit characters.
Note
^ inside [] means NOT, but outside [] means start of string.
Pro Tip
Character sets are useful for filtering and validating data.
Predefined Character Classes
These are shortcuts for commonly used character sets.
\d and \D
- \d matches digits
- \D matches non digits
\w and \W
- \w matches letters, digits, underscore
- \W matches everything else
\s and \S
- \s matches whitespace
- \S matches non whitespace
Caution
Always use raw strings when working with predefined classes to avoid escape issues.
Exercise
- Match all digits in a string
- Match all alphabets using range
- Use negation to remove numbers
- Use \w and \s in examples