Dictionaries not introduced but used in exercise in "Error and Exceptions" - & suggestiong

[evezeyl]

NB: Good first issue label (cannot be added because not in contributor list)

Exercise Reading error Messages - Lesson "Error and Exceptions"
(http://swcarpentry.github.io/python-novice-inflammation/09-errors/index.html)

• As dictionaries are not introduced previously in lesson (maybe a consequence of reducing the lesson) I suggest the following:

1. Moving this exercise at the end of the first lession section - before syntax errors (will be used to ensure that students have understood the traceback - and it is time for an exercice)
   Then this will also provide a good introduction to syntax errors (as the key error is a syntax error, and will naturly flow with the Caturday joke)
2. Provide a short introduction to exercise: so that students can read the exercise more easily without focussing on the fact that they have not encountered dictionaries before

This can be introduced (in a minimal way) by the instructor when introducing the exercise and should not take more than 1 min (avoiding extra material load for the course)

In this exercise we introduce a data structure that you did not previously encounter: dictionary.
In a dictionary: keys are associated to values: key-values pairs. Values can be of different types (ie:numbers, lists...) but keys must be unique and immutable (no lists). Dictionaries can be constructed using the following syntax:
a_dictionary = {'key1' : value1, 'key2': value2}

Dictionaries are not ordered, consequently we cannot access values using indexes, but we can acess values using their corresponding key. Ex:
print(a_dictionary['key1'])

All the best
Eve

[tobiashuste]

This sounds like a very reasonable suggestion to me.

Let me submit a PR for that.