import wx

app = wx.PySimpleApp()
frame = wx.Frame(None, title="Events")


def long_task():
    value = int(text.GetValue())
    new_text = str(sum(range(value + 1)))
    sizer.Add(wx.StaticText(frame, -1, label=new_text))
    sizer.Layout()

def press_button_function(event):
    long_task()
    
    
sizer = wx.BoxSizer(wx.VERTICAL)
text = wx.TextCtrl(frame, -1, "10")
button = wx.Button(frame, -1, "OK")
button.Bind(wx.EVT_BUTTON, press_button_function)

sizer.Add(text)
sizer.Add(button)

frame.SetSizer(sizer)
frame.Show()
app.MainLoop()