title: WooCommerce: get and set shipping & billing address's postcode
body: <p>How do I set/get the Postcode(Zip-code) in woocommerce? Is there a function for this?</p>
  
  <p>ie., can I set the zip code through any function?</p>
  
  <p>I would also like to know, how to populate this field with my data(say 546621) if the user is not logged in?</p>