Lecture Notes for CPSC 121 Fall 2012: Dictionaries and Exam Overview, Study notes of Computer Science

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Today

• Exam overview
• Dictionaries

Reading

• Ch 18 (Dictionaries)

Homework

• HW 11 due
• Reading assignment out
• Extra credit out

Exam 3 overview

Basics

• 10% of final grade
• closed book, notes, computer, etc.
• 5 multi-part questions

Topics

• Slices
• Boolean values
• Comparison operators (==, <=, >=, <, >, !=)
• Logical operators (and, or, not)
• Conditionals (if, if-else, if-elif, if-elif-else)
• While loops
• Flow charts

Note:

• tuples and dictionaries will be on the final
• so final will have some new stuff, but mostly old stuff

Dictionaries

Every key is unique in a dictionary

• For example:

d = {’a’: 1, ’b’: 2, ’a’: 3}

d {’a’: 3, ’b’: 2}

• Note the + operator is not supported

Dictionary operations

Dictionaries support many of the same operations as lists

d = {’a’: 1, ’b’: 2, ’c’: 3}

d[’a’] # subscript 1

d[’d’] = 1 # add a key-value pair d {’a’: 1, ’b’: 2, ’c’: 3, ’d’: 1}

d[’a’] = 2 # set a key value d {’a’: 2, ’b’: 2, ’c’: 3, ’d’: 1}

d.get(’a’) 2

d.get(’e’, 0) # alt value 0

’a’ in d # key in dictionary True

’e’ in d False

’e’ not in d True