Using character class [...]
Q
What is a character class? How to specify a character class in a regular expression?
How to write a regular expression using character classes to capture 7 digits phone numbers from this example string "123-4567, 123 4567 or 1234567"?
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A
A character class allows a set of possible characters, rather than just a single character, to match at a particular point in a regex. Character classes are denoted by brackets [...] , with the set of characters to be possibly matched inside.
Here are some examples of character classes:
[bcr]at # matches 'bat', 'cat', or 'rat' [yY][eE][sS] # match 'yes' in a case-insensitive way
The regular expression using character classes to capture 7-digit phone numbers from a text file:
[0123456789]{3}[- ]?[0123456789]{4}
[0123456789] - character class of any decimal digits
{3} - repeating 3 times
[- ]? - '-', ' ' or no character
2013-02-02, 2820👍, 0💬