Add generator expr.s to Scala for Python Devs

Author: smheidrich

_overviews/scala3-book/scala-for-python-devs.md

@@ -40,7 +40,7 @@ At a high level, Scala shares these *similarities* with Python:
 - Both have a relatively simple, concise syntax
 - Both support a [functional style of programming][fp-intro]
 - Both are object-oriented programming (OOP) languages
-- Both have comprehensions: Python has list comprehensions and Scala has `for` comprehensions
+- Both have comprehensions: Python has list comprehensions, dict comprehensions and generator expressions and Scala has `for` comprehensions
 - Both languages have support for lambdas and [higher-order functions][hofs]
 - Both can be used with [Apache Spark](https://spark.apache.org) for big data processing
 - Both have a wealth of terrific libraries
@@ -693,6 +693,26 @@ Scala also has `match` expressions.
   </tbody>
 </table>
 
+### Lazily evaluated comprehensions:
+
+<table>
+  <tbody>
+    <tr>
+      <td class="python-block">
+        <code>from itertools import count
+        <br>all_squares = (n**2 for n in count())&nbsp; # generator expression
+        <br># all_squares: &lt;generator object &lt;genexpr&gt; at ...&gt;</code>
+      </td>
+    </tr>
+    <tr>
+      <td class="scala-block">
+        <code>val allSquares = for n &lt;- LazyList.from(0) yield n * n
+        <br>// allSquares: LazyList(&lt;not computed&gt;)</code>
+      </td>
+    </tr>
+  </tbody>
+</table>
+
 ### `match` expressions:
 
 <table>