A regular expression (also called a regex or regexp) is a pattern that can match a piece of text. The simplest form of regular expression is just a plain string, which matches itself. A regexp can match more than one string, and you create such a pattern by using some special characters. For example , the period character ( dot ) matches any character (except a newline), so the regular expression '.ython' would match both the string 'python' and the string 'jython'. It would also match strings such as 'qython', '+ython', or ' ython' (in which the first letter is a single space), but not strings such as 'cpython' or 'ython' because the period matches a single letter, and neither two nor zero . and this period is called a wildcard. (pattern) ? pattern is used to Escaping Special Characters (pattern)* pattern is repeated zero or more times (pattern)+ pattern is repeated one or more times (patt...