A big mess of changes for the first day

[MaybeJustJames]

Chapter 1: Introduction

• Briefly describe the help() functions

Chapter 2: Variables and operators

• Organisation
• Remove mention of the identity operator (is) because it's subtle in ways that aren't appropriate for beginners. This does unfortunately mean we're doing inappropriate comparisons to None but I think that's a small price to pay.

Chapter 4: Conditions

• Formatting and flesh out text
• Add a section asking students to find an indentation bug
• Merge sections describing else and elif and flesh out the explanation with an example in English and pseudocode

Chapter 5: Lists, Tuples, and Sets

• Minor text corrections and flesh out a little
• Avoid mentioning "dictionary"
• Summarise in intro with a table rather than text
• Add a distinct section on slicing
• Add a question for students about creating an empty set(). This is meant for them to discover a pitfall. The correct answer is set(), not {} which is a dict.
• Add section on unpacking and the unpacking operator *

Chapter 6: Loops

• Flesh out explanation of loops where students were confused in previous teaching sessions.
• Explain loop iteration with loop unrolling
• Emphasise reading for as for-each
• Subtly introduce iterables
• Emphasise enumerate() over raw indexing with a guided "example problem".
• Introduce the conventional use of _
• Highlight the danger of while
• Add an exercise demonstrating the danger of while.

Solutions

• Updated in line with the above changes

[tmuylder]

Merging all your wonderful suggestions. I've seen a couple of typos which I'll edit in a next commit after merging. Idem dito for the section on enumerate, might do some changes there.