title: Learning Python from Ruby; Differences and Similarities
body: <p>I know Ruby very well. I believe that I may need to learn Python presently. For those who know both, what concepts are similar between the two, and what are different?</p>
  
  <p>I'm looking for a list similar to a primer I wrote for <a href="http://phrogz.net/Lua/LearningLua_FromJS.html" rel="noreferrer">Learning Lua for JavaScripters</a>: simple things like whitespace significance and looping constructs; the name of <code>nil</code> in Python, and what values are considered "truthy"; is it idiomatic to use the equivalent of <code>map</code> and <code>each</code>, or are <em>mumble</em> <em>somethingaboutlistcomprehensions</em> <em>mumble</em> the norm?</p>
  
  <p>If I get a good variety of answers I'm happy to aggregate them into a community wiki. Or else  you all can fight and crib from each other to try to create the one true comprehensive list.</p>
  
  <p><strong>Edit</strong>: To be clear, my goal is "proper" and idiomatic Python. If there is a Python equivalent of <code>inject</code>, but nobody uses it because there is a better/different way to achieve the common functionality of iterating a list and accumulating a result along the way, I want to know how you do things. Perhaps I'll update this question with a list of common goals, how you achieve them in Ruby, and ask what the equivalent is in Python.</p>