title: KeyError building parametrized string containing ':'
body: <p>Let's say, I need to build a series of strings based on this pattern:</p>
  
  <pre><code>pattern="{app: }"
  </code></pre>
  
  <p>with an ultimate goal of generating the below sequence:</p>
  
  <blockquote>
    <p>"{app: MS Office }"</p>
    
    <p>"{app: Notepad }"
    etc.</p>
  </blockquote>
  
  <p>I'm trying to do that using the format method, like so</p>
  
  <pre><code>insert="MS Office"
  result=pattern.format(insert)
  </code></pre>
  
  <p>However, all I get back is </p>
  
  <blockquote>
    <p>KeyError: 'app'</p>
  </blockquote>
  
  <p>It does look like the error is caused by Python misinterpreting the colon in the pattern, but what how do I get around it? I do need the colon.</p>
  
  <p>Thanks.</p>
  
  <p>. </p>