Lesson 3: Matching Digits in Regular Expressions

The \d metacharacter is a cornerstone in regex to identify digits in a string. Standing for "digit", it matches any single numeral from 0 to 9, providing a clean and straightforward way to locate numerical data. For example, \d will match any single digit in a string such as the '3' in  abc3def .

Combining \d with Quantifiers

To extend its functionality, \d can be used with quantifiers to match specific numbers of consecutive digits. For example, \d{3} would match any sequence of three digits, like  123  in  a123b . Meanwhile, \d+ will match one or more digits, like  4567  in  abc4567def .

Negating \d: Matching Non-digits

Sometimes, you might want to match non-digit characters, and for such purposes, the negation of \d, i.e., \D comes into play. \D will match any character that is not a digit, enhancing your matching capability to non-numerical data.