title: Joining elements of a list with a character
body: <p>Suppose I have the following list: </p>
  
  <pre><code>f=[('soybean', 'vegetable_oil'), ('bay', 'smoke'), ('gelatin', 'watermelon')]
  </code></pre>
  
  <p>I want to join each element such that I get </p>
  
  <pre><code>['soybean:vegetable_oil', 'bay:smoke', 'gelatin:watermelon']
  </code></pre>
  
  <p>To do that I do the following: </p>
  
  <pre><code>list=[]
  for i in f:
      s=':'
      list=s.join(f)
      print(list)
  </code></pre>
  
  <p>But thus returns:</p>
  
  <pre><code>TypeError: sequence item 0: expected string, tuple found
  </code></pre>
  
  <p>I realised also there is a similar question <a href="https://stackoverflow.com/questions/4874514/joining-elements-of-a-list">here</a> but when I do </p>
  
  <pre><code>':'.join(str(d) for d in f)
  </code></pre>
  
  <p>I get: </p>
  
  <pre><code>"('soybean', 'vegetable_oil'):('bay', 'smoke'):('gelatin', 'watermelon')"
  </code></pre>
  
  <p>which is not what I am after, I wonder what am I doing wrong here? </p>