Data, Variables, and Operators

CS 110

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Announcements

• Keep an eye out for Tutorial Team assignments tomorrow afternoon
• Reminder: Tutorial 1 is on Wednesday!
• Make sure to watch the pre-recorded lecture BEFORE coming to class on Wed. In order to get attendance credit you need BOTH watch the video AND attend.
• Office hours schedule available via Canvas
• Didn’t get a grade for MQ0 - check edSTEM! Had trouble with EX0? Keep an eye out for a Canvas message from me this afternoon.
• Overview of this Week
• Monday - Operators and Variables in Python
• Wednesday - Functions in Python (Pre-Recorded - Out-of-Class MQ 1) + Tutorial 1
• Friday - Writing our Own Functions + In-Class MQ 2
• Ex 1 - Due at 11:59pm on Canvas

A typical week…

Monday - Attend lecture, take a look at tutorial, and homework

Tuesday - Watch the pre-recorded lecture for Wednesday; peruse the tutorial

Wednesday - Come to the tutorial session, try your best to iron out all of your questions; see if you can do any of the HW

Thursday - by now, you should have a strong sense of how long it will take you to complete HW Exercise; if you need more time, apply for late penalty waiver

Friday - come to class, participate in MQ activities; finish up HW

Sat/Sun - take the weekend off

Resources available throughout the week: Canvas, Class, Office Hours, and edSTEM

Understanding the Words / Atoms of Programming

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Python is made up of different kinds of “words”, which can be used to construct sentences and paragraphs (statements and code blocks). Some types of ‘words’ in Python include:

• pieces of data like numbers, words, images, etc.
• operators are symbols that perform actions
• variables are containers that can hold data
• functions are blocks of code encased inside a function name
• reserved words (special words in python)
• modules

The first rule of programming!

Python will only do something you ask it to.

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Data Representation

How we represent pieces of data in Python

2

two

2.0

Data Types

data come in different flavors we call data types

2

two

2.0

2

two

2.0

Data Types

integer (int)

2

two

2.0

Data Types

integer (int)

2

"two"

2.0

Data Types

string (str)

integer (int)

2

"two"

2.0

Data Types

string (str)

float (float)

Variables

Named containers that allow us to store and access data in Python.

Variables

• Variables are named containers for storing and/or referencing data
• You assign values to variables using the assignment operator (equal sign)

variable_name = piece_of_data

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Variables

Turn the following statement into a sentence:

�favorite_cookie = "oreo"�

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Variables

Turn the following statement into a sentence:

�favorite_cookie = "oreo"�

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Variables

Turn the following statement into a sentence:

�favorite_cookie = "oreo"�

Assign the text "oreo" to a container called favorite_cookie.

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Variables

Turn the following statement into a sentence:

�favorite_cookie = "oreo"�

Assign the text "oreo" to a container called favorite_cookie.

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Big Idea: Our goal for any line of Python we write is to be able to explain what it does in plain english.

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Naming Variables

• Variable names in Python can be any length and can consist of:
• uppercase and lowercase letters (A-Z, a-z)
• digits (0-9)
• and the underscore character (_).
• The first character of a variable name cannot be a digit.

Example 1:

favorite_cookie = "oreo"

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Example 2:

1st_cookie = "oreo"

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Operators

Symbols that perform operations on inputs which we call operands.

Arithmetic Operators

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Example: Evaluate this expression (operator)

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4 * 6

operand

operand

operator

Example: Evaluate this expression (operator)

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4 * 6

4

operand

6

operand

*

operator

Example: Evaluate this expression (operator)

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4 * 6

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4

operand

6

operand

*

operator

Arithmetic Operators

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Operator Precedence

Python evaluates expressions as is done in mathematics. After precedence rules, expressions are evaluated left to right.

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Order of Operations

16 - 2 * 5 // 3 + 1

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Order of Operations

16 - 2 * 5 // 3 + 1

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Order of Operations

16 - 2 * 5 // 3 + 1

�

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10

16 - 10 // 3 + 1

�

Order of Operations

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16 - 10 // 3 + 1

�

Order of Operations

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16 - 10 // 3 + 1

�

Order of Operations

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3

16 - 3 + 1

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Order of Operations

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16 - 3 + 1

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Order of Operations

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16 - 3 + 1

�

Order of Operations

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13

13 + 1

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Order of Operations

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14

�

Order of Operations

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Examples

Example 02_arithmetic_operators.py

String Operators

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