The caret loses its special meaning if it is not the first character of the set. It does not match the empty string.For example, akm matches any character except "a", "k", or "m". If the first character of a character set is the caret (^), the regular expression matches any character except those in the set. A hyphen in a character set indicates a range of characters for example, a-z matches any single lowercase letter. For example, "" matches an "a", "k", or "m".
The corresponding escape codes are \r and \n.Ī one-character character set that matches any of the characters in that set. To match any character except a newline, use, which excludes the ASCII carriage return and line feed codes. Multiple capturing groups can have the same nameĪ backslash followed by any special character matches the literal character itself, that is, the backslash escapes the special character.For example, "+" matches the plus sign, and "Ī period matches any character, including newline. (?P=name) (Python-style named backreference) (?Pregex) (Python-style named capturing group \k'name' (.NET-style named backreference)
(?'name'regex) (.NET-style named capturing group) (?regex) (.NET-style named capturing group) (?ismxn:group) (mode modifiers local to group) ? after any of the above quantifiers to make it "lazy"īackreferences non-existent groups are an errorīackreferences to failed groups also fail \Y (NOT at the beginning or end of a word) \B (NOT at the beginning or end of a word) \Q.\E escapes a string of character class metacharacters \Q.\E escapes a string of metacharactersīackslash escapes one character class metacharacter The special character * after the closing square bracket specifies to match zero or more occurrences of the character set. The regular expression * matches any sequence of letters that starts with an uppercase letter and is followed by zero or more lowercase letters. The regular expression matches "BIG", "BAG", "BIN", and "BAN".
This regular expression matches "B", followed by an "I" or "A", followed by a "G" or "N". If you specified the regular expression as "B", the concatenation of character sets creates a regular expression that matches the corresponding concatenation of characters in the search string. The regular expression " BG " matches the strings "BIG", "BAG", and "BUG", but does not match the string "BOG". For example matches any single character that is not a capital letter. In a character set a ^ character negates the following characters. In the character set, a hyphen indicates a range of characters, for example will match any one capital letter. For example, the regular expression " " specifies to match any single uppercase or lowercase letter. The pattern within the brackets of a regular expression defines a character set that is used to match a single character.
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