Azure CLI - az storage file delete-batch: pattern for all but one specific file

I'm trying to delete all files from an Azure Storage File share and exclude one specific file name. I just can't figure out the pattern.

I've tried this but the pattern doesn't match anything now.

az storage file delete-batch --source "https://myst.file.core.windows.net/myshare" --sas-token $sastoken --pattern "[!importantfile.py]"

You need to add the pattern parameter in single quotes as shown in the below

az storage file delete-batch --source "https://myst.file.core.windows.net/myshare" --sas-token $sastoken --pattern '[!importantfile.py]*' 

• If you have similar files in the file share like (test.json.test1.json) ,using
  az storage delete-batch with pattern filter wont be possible to exclude the deletion of a particular file.

• Reference SO thread how to use pattern in the az storage blob delete-batch

Alternatively, if want a particular file to be excluded from deletion in file share you can use the below power shell script

connect-azaccount
$accountName = '<accountname>';
$accountKey = '<accountkey>';
$myshare = '<file sharename >';
$notremovalfile = '<file that need to be excluded from deletion>';

 $filelist = az storage file list -s $myshare --account-name $accountName --account-key $accountKey

    $fileArray = $filelist|ConvertFrom-Json 


    foreach ($file in $fileArray)
    {
       if($file.name -ne $notremovalfile)
       {
            Write-Host $file.name
            az storage file delete --account-name $accountName --account-key $accountKey -s $myshare -p $file.name
            Write-Host "deleting $file.name"
        }
          

    }