title: Replacing digits with str.replace()
body: <p>I want to make a new string by replacing digits with <code>%d</code> for example:</p>
  
  <pre><code>Name.replace( "_u1_v1" , "_u%d_v%d") 
  </code></pre>
  
  <p>...but the number <code>1</code> can be any digit for example <code>"_u2_v2.tx"</code></p>
  
  <p>Can I give <code>replace()</code> a wildcard to expect any digit? Like <code>"_u"%d"_v"%d".tx"</code></p>
  
  <p>Or do I have to make a regular expression?</p>