script to transform/filter postcodes.csv - choose columns, filter by postcode district(s) and weather in-use or not.

transform_postcodes.sp1

# https://www.doogal.co.uk/files/postcodes.zip
# 0  Postcode      # 21 Lower layer super output area  # 42 Plus Code
# 1  In Use?       # 22 Rural/urban                    # 43 Average Income
# 2  Latitude      # 23 Region                         # 44 Sewage Company
# 3  Longitude     # 24 Altitude                       # 45 Travel To Work Area
# 4  Easting       # 25 London zone                    # 46 ITL level 2
# 5  Northing      # 26 LSOA Code                      # 47 ITL level 3
# 6  Grid Ref      # 27 Local authority                # 48 UPRNs
# 7  County        # 28 MSOA Code                      # 49 Distance to sea
# 8  District      # 29 Middle layer super output area # 50 LSOA21 Code
# 9  Ward          # 30 Parish Code                    # 51 Lower layer super output area 2021
# 10 District Code # 31 Census output area             # 52 MSOA21 Code
# 11 Ward Code     # 32 Index of Multiple Deprivation  # 53 Middle layer super output area 2021
# 12 Country       # 33 Quality                        # 54 Census output area 2021
# 13 County Code   # 34 User Type                      # 55 IMD decile
# 14 Introduced    # 35 Last updated                   # 56 Constituency Code 2024
# 15 Terminated    # 36 Nearest station                # 57 Constituency Name 2024
# 16 Parish        # 37 Distance to station            # 58 Property Type
# 17 National Park # 38 Postcode area                  # 59 Roads
# 18 Population    # 39 Postcode district              # 60 FixPhrase
# 19 Households    # 40 Police force                   # 61 Rural/urban 2021
# 20 Built up area # 41 Water company

Add-Type -AssemblyName Microsoft.VisualBasic

# columns to export (see table above for id)
$columns = @(0, 4, 5)

# postcode districts to export
$postcodes = @("CB1","CB2","CB23","CB24","CB3","CB4","PE27","PE28","PE29")

# filter out-of-use postcodes
$filter = $true

$source = Get-Item "$PSScriptRoot\postcodes.csv"
$output = "$PSScriptRoot\output.csv"

$parser = [Microsoft.VisualBasic.FileIO.TextFieldParser]::new($source)
$writer = [System.IO.StreamWriter]::new($output)

try {
    $parser.TextFieldType = [Microsoft.VisualBasic.FileIO.FieldType]::Delimited
    $parser.SetDelimiters(",")
    $parser.HasFieldsEnclosedInQuotes = $true

    $headers = $parser.ReadFields()

    $selected = $columns | ForEach-Object { $headers[$_] }
    $writer.WriteLine($selected -join ",")

    while (!$parser.EndOfData) {
        $fields = $parser.ReadFields()
        if ($filter -and ($fields[1] -eq "No")) { continue }
        if (($postcodes -contains $fields[39])) {
            $selected = $columns | ForEach-Object { $fields[$_] }
            $writer.WriteLine($selected -join ",")
        }
    }
} 
finally {
    $parser.Dispose()
    $writer.Dispose()
}