This document covers variables in Python including: - What variables are and how to name them correctly using letters, digits and underscores while avoiding keywords - Creating variables by assigning a value using the equal sign - Reassigning values to existing variables and using shortcut operators - The key points that variables store values in memory, have unique names, Python is dynamically typed, and how to output text and variables.

1. Module 1
operations, basic operators,data types, variables,
basic input-output
Variables

2. Module 1 Variables
What are variables?
Variable name
be composed of
uppercase or
lowercase letters,
digits, and the
character _
begin with a letter;
the underscore
character is a letter;
upper- and lower-
case letters are
treated as different;
not be any of
Python's reserved
words.

3. Module 1 Variables
Correct & incorrect variable names
Correct, but not always
convenient:
Incorrect
MyVariable i t34 Exchange_Rate
days_to_christmas TheNameIsSoLongThatYouWillMakeMistakesWithIt
10t Exchange Rate

4. Module 1 Variables
Keywords
neither
for your
variables
nor
functions
Keyword
s
'False', 'None', 'True', 'and', 'as',
'assert', 'break', 'class', 'continue', 'def',
'del', 'elif', 'else', 'except', 'finally', 'for',
'from', 'global', 'if', 'import', 'in', 'is',
'lambda', 'nonlocal', 'not', 'or', 'pass',
'raise', 'return', 'try', 'while', 'with',
'yield'

5. Module 1 Variables
Creating variables
use the
name of
the
desired
variable
the equal
sign (=)
the value
var = 1
account_balance = 1000.0
client_name = 'John Doe'
print(var, account_balance, client_name)
print(var)
1 1000.0 John Doe
1

6. Module 1 Variables
Assigning a new value to an already existing
variable
var = 1
print(var)
var = var + 1
print(var)
1
2
var = 100
var = 200 + 300
print(var)
500
a = 3.0
b = 4.0
c = (a ** 2 + b ** 2) ** 0.5
print("c =", c)
c = 5.0

7. Module 1 Variables
Shortcut operators
x *= 2
• x = x * 2
sheep += 1
• sheep = sheep + 1
variable op= expression
• variable = variable op expression

8. Module 1 Variables
Key takeaways
1
• A variable is a named location reserved to store values in the memory
2
• Each variable must have a unique name - an identifier
3
• Python is a dynamically-typed language
4
• Using compound assignment operators
5
• Assigning new values to already existing variables
6
• Combining text and variables using the + operator

9. Module 1 Variables
LAB Practice
4. Variables
5. Variables: a simple converter
6. Operators and expressions