Check U.K Postcode for Validation [duplicate]

Question

I need to check the U.K postcode against a list.

The U.K postcode is of a standard format but the list only contains the outward section that I need to check against.

The list contains a series of outward postcode with also some data relating to this outward postcode, so for example

AL     St Albans
B      Birmingham
BT     Belfast
TR     Taunton
TR21    Taunton X
TR22    Taunton Y

My aim is that when I get a postcode, for example B20 7TP, I can search and find Birmingham.

Any ideas??

The question is different to the ones referred to as possible answers, but in my case I need to check a full postcode against just the outward postcode.

Answer 1

If you have the whole postcode and only want to use the outcode, remove the last three characters and use what remains. All postcodes end with the pattern digit-alpha-alpha, so removing those characters will give the outcode; any string that does not fit that pattern or that does not give a valid outcode after removing that substring is not a valid postcode. (Source)

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If you're willing to take on an external (and Internet-based) dependency, you could look at using something like https://postcodes.io, in particular the outcodes section of that API. I have no affiliation with postcodes.io; I just found it after a Google.

Per the documentation, /outcodes will return

• the outcode
• the eastings
• the northings
• the andministrative counties under the code
• the district/unitary authories under the code
• the administrative/electoral areas under the code
• the WGS84 logitude
• the WGS84 latitude
• the countries included in the code
• the parish/communities in the code

For reference, a call to /outcodes/TA1 returns:

{
  "status": 200,
  "result": {
    "outcode": "TA1",
    "longitude": -3.10297767924529,
    "latitude": 51.0133987332761,
    "northings": 124359,
    "eastings": 322721,
    "admin_district": [
      "Taunton Deane"
    ],
    "parish": [
      "Taunton Deane, unparished area",
      "Bishop's Hull",
      "West Monkton",
      "Trull",
      "Comeytrowe"
   ],
    "admin_county": [
      "Somerset"
    ],
    "admin_ward": [
      "Taunton Halcon",
      "Bishop's Hull",
      "Taunton Lyngford",
      "Taunton Eastgate",
      "West Monkton",
      "Taunton Manor and Wilton",
      "Taunton Fairwater",
      "Taunton Killams and Mountfield",
      "Trull",
      "Comeytrowe",
      "Taunton Blackbrook and Holway"
    ],
    "country": [
      "England"
    ]
  }
}

If you have the whole postcode, the /postcodes endpoint will return considerably more detailed information which I will not include here, but it does include the outcode and the incode as separate fields.

I would, of course, recommend caching the results of any call to a remote API.