Issue: Zebra printer print label with previous data

Question

I'm new to Zebra printers and still learning about ZPL. I need help on printing label using USB Connection from VB.net to GK420t printer.

^XA
^CF0,30,28^FO110,23^FD{Hello}^FS 
^CF0,24,26^FO110,58^FD{World}^FS
^XZ 

Public Function GetUSBPrinters() As List(Of DiscoveredPrinter)
    Dim printerList As List(Of DiscoveredPrinter) = New List(Of DiscoveredPrinter)()
    Try
        For Each usbPrinter As DiscoveredUsbPrinter In UsbDiscoverer.GetZebraUsbPrinters()
            printerList.Add(usbPrinter)
            Console.WriteLine(usbPrinter)
        Next

    Catch e As ConnectionException
        Console.WriteLine($"Error discovering local printers: {e.Message}")
    End Try

    Console.WriteLine("Done discovering local printers.")
    Return printerList
End Function

Public Sub SendDataToPrinter()
    zplcode = zplcode.Replace("{Hello}", "Hello")
    zplcode = zplcode.Replace("{World}", "World")

    Try
        Dim printerList As List(Of DiscoveredPrinter) = GetUSBPrinters()
        If printerList.Count > 0 Then
            Dim discoveredPrinter As DiscoveredPrinter = printerList(0)
            Dim connection As Connection = discoveredPrinter.GetConnection()
            connection.Open()
            connection.Write(Encoding.UTF8.GetBytes(zplcode))

        End If
    Catch ex As Exception
        Console.WriteLine("No Printers found to print to.")
    End Try
End Sub

The scenario would be like this: When I first time print Label A, it comes out one Label A. But when I try to print another label which is Label B, it will be printed Label B and Label A. And the cycle goes again.

Is there any solutions or anyone experiences these? Thanks in advance.

Answer 1

Besides the good answer provided by @Peter Leimbigler, as an alternative solution, converting the Date column to a string before applying the Style prevents the Styler formatter from adding timestamp.

df['Date'] = df['Date'].astype(str)

Using Peter's example:

# Example data
df = pd.DataFrame({'Date': pd.date_range('2020-01-01', 
                                         '2020-01-05', 
                                         freq='d'),
                   'Value': list(range(-2, 3))})

# Example color function
def f(v):
    return 'color: red;' if v < 0 else None

# Converting the Date column to a string before applying the Style
df['Date'] = df['Date'].astype(str)

df.style.applymap(f, subset='Value')