Powershell - Empty entries in CSV - powershell

Question

I don't have much experience with CSV, so apologies if I'm really blind here.
I have a basic CSV and script setup to test this with. The CSV has two columns, Letter and Number. Letter goes from A-F and Number goes from 1-10. This means that Number has more rows than Letter, so when running the following script, the output can sometimes provide an empty Letter.
$L = ipcsv ln.csv | Get-Random | Select-Object -ExpandProperty Letter
$N = ipcsv ln.csv | Get-Random | Select-Object -ExpandProperty Number
Write-Output $L
Write-Output $N
Some outputs come out as
B
9
while others can come out as
5
I don't know whether the issue is my script not ignoring empty lines or my CSV being written incorrectly, which is posted below.
Letter,Number
A,1
B,2
C,3
D,4
E,5
F,6
,7
,8
,9
,10
What's my issue here and how do I go about fixing it?

Answer 1

Your asking for a random object from your CSV, not a random letter. Since some of the lines are missing a letter, you might end up picking one that has an empty Letter-value.
If you want to pick any line with a letter, you need to filter the rows first to only pick from the ones with a value. Also, you sould avoid reading the same file twice, use a varible
#$csv = Import-CSV -Path ln.csv
$csv = #"
Letter,Number
A,1
B,2
C,3
D,4
E,5
F,6
,7
,8
,9
,10
"# | ConvertFrom-Csv
$L = $csv | Where-Object { $_.Letter } | Get-Random | Select-Object -ExpandProperty Letter
$N = $csv | Where-Object { $_.Number } | Get-Random | Select-Object -ExpandProperty Number
Write-Output $L
Write-Output $N
CSV migtht not be the best solution for this scenario. Ex. you could store these as arrays in the script, like:
$chars = [char[]](65..70) #A-F uppercase letters
$numbers = 1..10
$L = $chars | Get-Random
$N = $numbers | Get-Random
Write-Output $L
Write-Output $N

Answer 2

Import-Csv turns each line into an object, with a property for each column.
Even though one or more property values may be empty, the object still exists, and Get-Random has no reason determine that an object with a certain property (such as Letter) having the value "" (ie. an empty string), should not be picked.
You can fix this by expanding the property values first, then filter for empty values and then finally pick the random value from those that weren't empty:
$L = ipcsv ln.csv |Select-Object -ExpandProperty Letter |Where-Object {$_} |Get-Random
$N = ipcsv ln.csv |Select-Object -ExpandProperty Number |Where-Object {$_} |Get-Random