The re module supports several metacharacters that have special meanings in regular expressions. Here are some of the most commonly used metacharacters:

  • . (dot): Matches any character except a newline character.

  • ^ (caret): Matches the beginning of a line or string.

  • $ (dollar sign): Matches the end of a line or string.

  • * (asterisk): Matches zero or more occurrences of the preceding character or group.

  • + (plus sign): Matches one or more occurrences of the preceding character or group.

  • ? (question mark): Matches zero or one occurrence of the preceding character or group.

  • [] (brackets): Matches any one of the characters inside the brackets.

  • | (pipe): Matches either the expression before or after the pipe.

  • () (parentheses): Groups a series of characters or expressions together, and captures the matched substring for later use.

  • \ (backslash): Escapes a special character, or indicates a special sequence.

These metacharacters can be used to build complex patterns that match specific types of text. For example, the pattern [A-Za-z]+ would match one or more occurrences of any uppercase or lowercase letter, while the pattern \d{3}-\d{2}-\d{4} would match a social security number in the format of 123-45-6789.

It's important to note that some characters may have special meanings in certain contexts. For example, in a character class (i.e. inside square brackets), the caret (^) has a different meaning than outside a character class. In a character class, the caret negates the class, so [^abc] matches any character that is not a, b, or c. Outside of a character class, the caret matches the beginning of a line or string.

To match a metacharacter as a literal character, it can be escaped with a backslash. For example, to match a literal period (.), you would use the pattern \..