Selenium (python) locating button relative to another div with Id

I need to click on the Ok button on a page (HTML code snippet hereunder). The button itself does not have an Id and its XPath changes. It can be any of the following:

/html/body/div[3]/div[3]/div/button
/html/body/div[4]/div[3]/div/button
/html/body/div[5]/div[3]/div/button

The only stable locator I can find in the page is the noresultsfound Id of the div before the div that contains the button as a child div.

I am unable to guess which Selenium locator I could use to RELIABLY click on the button.

<div class="ui-dialog ui-widget ui-widget-content ui-corner-all ui-front ui-dialog-buttons ui-draggable ui-resizable" tabindex="-1" role="dialog" aria-describedby="noresultsfound" aria-labelledby="ui-id-1" style="position: absolute; height: auto; width: 300px; top: 850px; left: 365px; display: block;">
   <div class="ui-dialog-titlebar ui-widget-header ui-corner-all ui-helper-clearfix"><span id="ui-id-1" class="ui-dialog-title">Attenzione</span><button class="ui-button ui-widget ui-state-default ui-corner-all ui-button-icon-only ui-dialog-titlebar-close" role="button" aria-disabled="false" title="close" style="display: none;"><span class="ui-button-icon-primary ui-icon ui-icon-closethick"></span><span class="ui-button-text">close</span></button></div>
   <div id="noresultsfound" class="ui-dialog-content ui-widget-content" style="width: auto; min-height: 0px; max-height: none; height: auto;">
      <p>Nessun risultato trovato</p>
   </div>
   <div class="ui-dialog-buttonpane ui-widget-content ui-helper-clearfix">
      <div class="ui-dialog-buttonset"><button type="button" class="ui-button ui-widget ui-state-default ui-corner-all ui-button-text-only" role="button" aria-disabled="false"><span class="ui-button-text">Ok</span></button></div>
      <p style="border-top: 1px solid #bcbcbc; margin-top:10px; padding-top:5px;color:#054a6c;font-style:italic;font-weight:bold;font-size:0.7em;margin-bottom: 0px;">Il portale è progettato per una visualizzazione ottimale con i seguenti browser:<br>Internet Explorer (V9), Chrome (V 35.0.1916.114m) e Firefox (V28 e29)</p>
   </div>
   <div class="ui-resizable-handle ui-resizable-n" style="z-index: 90;"></div>
   <div class="ui-resizable-handle ui-resizable-e" style="z-index: 90;"></div>
   <div class="ui-resizable-handle ui-resizable-s" style="z-index: 90;"></div>
   <div class="ui-resizable-handle ui-resizable-w" style="z-index: 90;"></div>
   <div class="ui-resizable-handle ui-resizable-se ui-icon ui-icon-gripsmall-diagonal-se" style="z-index: 90;"></div>
   <div class="ui-resizable-handle ui-resizable-sw" style="z-index: 90;"></div>
   <div class="ui-resizable-handle ui-resizable-ne" style="z-index: 90;"></div>
   <div class="ui-resizable-handle ui-resizable-nw" style="z-index: 90;"></div>
</div>

My code so far is like the following:

try:  # things are good when the following error modal window is NOT found
  digram_notfound = DRIVER_WAIT.until(
                EC.visibility_of_element_located((By.ID, "noresultsfound"))
                )
  if digram_notfound:
                click_xpath(driver, "/html/body/div[4]/div[3]/div/button")       
except  TimeoutException:
  do useful stuff here

but as I said it fails on those pages where the XPath is different.

Is there a way of writing a locator anchored to the Id and find the button to click relative to that? Thanks

Answer

<div class="ui-dialog-buttonset"><button type="button" class="ui-button ui-widget ui-state-default ui-corner-all ui-button-text-only" role="button" aria-disabled="false"><span class="ui-button-text">Ok</span></button></div>

There are many selectors you could try for this element.

//button[./span[@class='ui-button-text' and text()='Ok']]
//div[@class='ui-dialog-buttonset']/button