Test a URL!

test-url.ps1

Function Test-Url {
    [CmdletBinding()]
    
    param (
        [Parameter(Mandatory=$true)]
        [String] $Url
    )

    Process {
        if ([system.uri]::IsWellFormedUriString($Url,[System.UriKind]::Absolute)) {
            $true
        } else {
            $false
        }
    }
}

#Here is how we use it
$doc = Invoke-WebRequest -Uri 'https://www.python.org/downloads'
foreach ($href in ($doc.links.href -ne '')) {
    if (Test-Url -Url $href) {
        $href
    }   
}