Understand “regex” in under fives minutes.
Regex (regular expressions), are expressions used to match specific patterns in strings.
Here’s an example: How can we validate whether our user inputs a valid birth date year (we’re not checking whether the year is before today’s current year).
Non-regex way:
if string is not of length four: return False for each character in the string if character is not a digit: return False return True
regex way
if string matches regex
^\\d{4}$then return True, else False
Below you’ll find a visual aid to understand this regex.
\\d here means digit.
{4} specifies that we’re looking for four of whatever precedes it, which is a digit.
(website used: https://www.regexplained.co.uk/)
^ specifies the start of a string.
$ specifies the end of as string.
Using ^ and $ are important as shown below. We get a match for the string on the fourth line because we aren’t specifying that the string should start with four digits.