title: Python: understanding lambda expressions with two variables
body: <p>While looking up concise ways to calculate the product of a list, I was a little confused by this <a href="https://stackoverflow.com/questions/595374/whats-the-python-function-like-sum-but-for-multiplication">response</a>. Here's the code in question:</p>
  
  <p><code>reduce(lambda x,y:x*y,[3,4,5])</code></p>
  
  <p>Can someone explain why this works? I'm familiar with using <code>lambda</code> expressions involving one variable (e.g. when using a custom compare function for <a href="https://stackoverflow.com/questions/72899/how-do-i-sort-a-list-of-dictionaries-by-values-of-the-dictionary-in-python">sorting</a>) but am confused why and how this works. </p>