1. Nate Brunelle Today: Dictionaries
CS1110
Nate Brunelle
Today: Dictionaries

2. Questions?

3. Tips for fixing bugs in code
Know what your code should do
Read error messages
Believe the error message
Print every variable
Binary search
Test more
Look for “code coverage”

4. Binary search Start: a line you know is before the bug
End: a line you know is after the bug
Middle: the line halfway between start and end
Check whether Middle has the bug. If so, then Middle is the new End. Otherwise if Middle has no bug, then Middle is the new Start.
You just ruled out half of the remaining lines of code as the bad ones!
Keep going until you have only 1 line of code left. That one has the bug.

5. Test Cases Try winning: fun, f, u, n Capital: FUN, f, u ,n 1234, 1
Fun, fn,
Fun, x, x, x, x, x, x
F_n, n, _

6. Collections Order doesn’t matter, No Repetition
Order Matters, Repetition ok
Examples:
String
List
Tuple
Range
Counting starts at 0
collection[index] gives a specific value in the collection
Order doesn’t matter, No Repetition
Examples:
Set
Dict
Map
Table

7. Set
Things are unordered
Cannot have repetition

8. Dict
A set of key:value mappings
d = { }
d[‘name’] = 1
d[‘name’]

9. Dict
Somewhat like variables, somewhat like a list

10. Dict is like variables Gives names to values Create using =
Reassign using =
Easy to go from name to a value
Very hard to go from value to name

11. Dict is like a list Index to access members Index must be an int
Key to access members
Key can be any immutable type
No rules for values of keys
To add in a new thing: d[key] = …
Index to access members
Index must be an int
Indexes cannot be skipped
To add in a new thing: lst.append(…)