Identifier must begin either with the alphabet or with an underscore, it cannot start with a digit or any other special character, moreover, it can be followed by numbers.
gfg: valid identifier 123: invalid identifier _abc12: valid identifier #abc: invalid identifier
In this program, we use the
search () method of the regex module.
re.search (): this method either returns None (if the pattern does not match) or
re.MatchObject which contains information about the matching part of the string. This method stops after the first match, so it’s better for checking regular expressions than for extracting data.
Let’s take a look at a Python program to determine if a string is an identifier or not.
Valid Identifier Invalid Identifier Invalid Identifier