Regular expression to extract the year from a string

Question

This should be simple but i cant seem to get it going. The purpose of it is to extract v3 tags from mp3 file names in Mp3tag.

I have these strings I want to extract

Answer 1

A suggestion for a more generic solution, not sure if that is what you need. Valid years will always have the form 19xx or 20xx, and the years will be separated with a word-break character (something other than a number or a letter):

\b(19|20)\d{2}\b

This doesn't really care where in the tag the year appears. A simpler version that doesn't assume anything more than 4 digits in the year would be this expression:

\b\d{4}\b

The key here is the \b escape sequence, which matches any non-word character (word charaters are letters, digits and underscores), including parenthesis, of course.

Would also like to recommend this site: http://www.regular-expressions.info/

Answer 2

You're almost there with your regular expression.

What you really need is:

\s\((\d{4})\)$

Where:

• \s is some whitespace
• \( is a literal '('
• ( is the start of the match group
• \d is a digit
• {4} means four of the previous atom (i.e. four digits)
• ) is the end of the match group
• \) is a literal ')'
• $ is the end of the string

For best results, put into a function:

>>> def get_year(name):
...     return re.search('\s\((\d{4})\)$', name).groups()[0]
... 
>>> for name in "Test String 1 (1994)", "34 Test String 2 (1995)", "Test (String) 3 (1996)":
...     print get_year(name)
... 
1994
1995
1996

Answer 3

I'd go with

^(.*)\s\(([0-9]{4})\)$

(assuming all years have 4 digits, use [0-9]+ if you have an unknown number of digits, but at least one, or [0-9]* if there could be no digits)

Answer 4

You need to escape the parentheses. Also you can restrict that a year has only got 4 numbers:

^(.+)\s\(([0-9]{4})\)$

The year is in matchgroup 2.

Answer 5

You can use something like this \((\d{4})\)$. The first group will have your match.

Explanation

\(       # Match the character “(” literally
(        # Match the regular expression below and capture its match into backreference number 1
   \d       # Match a single digit 0..9
      {4}      # Exactly 4 times
)
\)       # Match the character “)” literally
$        # Assert position at the end of a line (at the end of the string or before a line break character)