update

Author: trayc7

_episodes/01-intro.md

@@ -187,7 +187,7 @@ You can run python in various tools. Perhaps the most straightforward is to use
 $ python
 ```
 ~~~
-Python 3.8.5 (default, Sep  4 2020, 02:22:02) 
+Python 3.8.8 (default, Feb 24 2021, 13:46:16) 
 [Clang 10.0.0 ] :: Anaconda, Inc. on darwin
 Type "help", "copyright", "credits" or "license" for more information.
 >>>

_episodes/02-datatypes.md

@@ -280,7 +280,7 @@ numbers["one"]
 Dictionaries work a lot like lists - except that you index them with *keys*.
 You can think about a key as a name for or a unique identifier for a set of values
 in the dictionary. Keys can only have particular types - they have to be
-"hashable". Strings, numeric types, and tuples are acceptable, but lists are not.
+"hashable", which means they don't change. Strings, numeric types, and tuples are acceptable, but lists are not.
 
 Here is a dictionary with natural numbers as keys. You access the values associated with each key, by providing the key in `[]`