Types, Expressions, & Variables - Cornell University

[Pages:23]Lecture 1

Types, Expressions, & Variables

About Your Instructor

? Director: GDIAC

? Game Design Initiative at Cornell

? Teach game design

? (and CS 1110 in fall)

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Overview, Types & Expressions

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Helping You Succeed in this Class

? Consultants. ACCEL Lab Green Room

? Daily office hours (see website) with consultants

? Very useful when working on assignments

? Piazza. Online forum to ask/answer questions

? Go here first before sending question in e-mail

? Office Hours. Talk to the professor

? Carpenter Hall Atrium on Tu Th 10-11 am

? Otherwise, in 4118 Upson Hall

? Open door policy (if door open, come in)

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Variables & Assignment

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Office Hours this Semester

classroom

Office Hours

Tue & Thu

10-11

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Variables & Assignment

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Getting Started with Python

? Designed to be used from the "command line"

? OS X/Linux: Terminal

? Windows: Command Prompt

? Purpose of the first lab

? Once installed type "python"

? Starts an interactive shell

? Type commands at >>>

? Shell responds to commands

This class uses Python 2.7.x

? Python 3 is too cutting edge

? Minimal software support

? Can use it like a calculator

? Use to evaluate expressions

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The Basics

integer

float (real number)

Values

42

12.345

"Hello!"

Types

string (of characters)

Expressions

34 * (23 + 14) 1.0 / 3.0

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"Hel" + "lo!"

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Python and Expressions

? An expression represents something

? Python evaluates it (turns it into a value)

? Similar to what a calculator does

? Examples:

? 2.3

Literal

(evaluates to self)

? (3 * 7 + 2) * 0.1

An expression with four literals and some operators

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Representing Values

? Everything on a computer reduces to numbers

? Letters represented by numbers (ASCII codes)

? Pixel colors are three numbers (red, blue, green)

? So how can Python tell all these numbers apart?

Memorize this definition!

? Type:

Write it down several times.

A set of values and the operations on them.

? Examples of operations: +, -, /, *

? The meaning of these depends on the type

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Overview, Types & Expressions

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