Module 1 Quick Reference Card

Python is CASE-SENSITIVE: print() works, Print() does NOT!

What is Python?

High-level: Handles complexity for you
Interpreted: Runs line by line
Dynamically typed: No type declarations
Indentation-based: Whitespace matters!

Created By

Guido van Rossum in 1991
Named after Monty Python (not the snake!)
We use Python 3 (Python 2 retired 2020)

The print() Function

            # Basic printing

            print("Hello, World!")

            # Multiple items (adds spaces)

            print("Age:", 25)

            # Math in print

            print("Sum:", 3 + 4)

            # Empty line

            print()

Comments

            # This is a comment

            print("Hi") # Inline comment

            # print("Commented out code")

Comments start with #
Python ignores everything after #
Use comments to explain why, not what

Strings (Text)

            # Single or double quotes

            "Hello"

            'Hello'

            # Apostrophes? Use double quotes

            "It's fun"

            # Quote marks? Use single quotes

            'She said "hi"'

Arithmetic Operators

Operator	Name	Example	Result
`+`	Addition	5 + 3	8
`-`	Subtraction	10 - 4	6
`*`	Multiplication	6 * 7	42
`/`	Division	15 / 4	3.75
`//`	Integer Div	15 // 4	3
`%`	Modulo	15 % 4	3
`**`	Power	2 ** 3	8

            / always returns float

            // rounds DOWN to int

Data Types (Preview)

Type	Name	Examples
int	Integer	42, -7, 0
float	Decimal	3.14, -0.5
str	String	"hello", '42'
bool	Boolean	True, False

            type(42)     # <class 'int'>

            type("42")   # <class 'str'>

The REPL

Read → Eval → Print → Loop

Start: type python in terminal
Exit: type exit() or quit()
Prompt: >>> means ready for input

Running Python

Script File

Save as filename.py
Run: python filename.py
In IDLE: press F5

File Naming Rules

Use .py extension
Lowercase + underscores
No spaces in names
Never name it python.py!

Useful Functions

            print()   # Display output

            type()    # Check data type

            help()    # Get documentation

            exit()    # Leave the REPL

Common Errors to Avoid

Print() instead of print() (case!)
Mismatched quotes: "hello'
Missing parentheses: print "hi"
Forgetting quotes around text
Naming file python.py
Not adding Python to PATH

🐍 Python Quick Reference Card