用于匹配 XX/YY 字符串但不匹配 XX/YY/ZZ 字符串的正则表达式

Question

I would like to try and match text that is in the form of

<some digits>/<some digits>

, but NOT

<some digits>/<some digits>/<some digits>

As an example, if the text is

01/21

or

1/21

I would like to match those, but not

1995/01/01

or

5/12/92

The background for this is that I am using Duckling to detect dates, and it detects dates like "12/21", but classifies this as MM/DD, whereas I want it to treat it as YY/MM, so I would like to correct these detections.

How would I do this? Thanks

Answer 1

Use

(?<!\d)(?<!\d/)\d+/\d+(?!/?\d)

See proof .

Explanation

--------------------------------------------------------------------------------
  (?<!                     look behind to see if there is not:
--------------------------------------------------------------------------------
    \d                       digits (0-9)
--------------------------------------------------------------------------------
  )                        end of look-behind
--------------------------------------------------------------------------------
  (?<!                     look behind to see if there is not:
--------------------------------------------------------------------------------
    \d                       digits (0-9)
--------------------------------------------------------------------------------
    /                        '/'
--------------------------------------------------------------------------------
  )                        end of look-behind
--------------------------------------------------------------------------------
  \d+                      digits (0-9) (1 or more times (matching
                           the most amount possible))
--------------------------------------------------------------------------------
  /                        '/'
--------------------------------------------------------------------------------
  \d+                      digits (0-9) (1 or more times (matching
                           the most amount possible))
--------------------------------------------------------------------------------
  (?!                      look ahead to see if there is not:
--------------------------------------------------------------------------------
    /?                       '/' (optional (matching the most amount
                             possible))
--------------------------------------------------------------------------------
    \d                       digits (0-9)
--------------------------------------------------------------------------------
  )                        end of look-ahead

Answer 2

Just use \d{1,2}\/\d{1,2} . You can try your regular expressions here: https://regex101.com