Core Python Syntax and Data Types

Lesson Overview

This lesson provides a concise refresher on essential Python syntax and data types. It is designed for learners who have some prior exposure to Python and want to strengthen their understanding before moving on to more complex coding tasks. We will clarify how variables work, review Python’s main data structures, and highlight common mistakes to avoid.

1. Python Syntax Basics

Indentation

Python uses indentation to define code blocks.
Indentation is usually 4 spaces (not tabs).

if True:
    print("This is indented correctly.")

Comments

Use # for single-line comments.
Use triple quotes (''' or """) for multi-line comments or docstrings.

# This is a single-line comment
"""
This is a
multi-line comment
"""

Variables

Variables are created when you assign a value to a name.
No need to declare the type explicitly.

x = 5
name = "Alice"

2. Core Data Types

Numbers

Integers: Whole numbers (e.g., 7, -3)
Floats: Decimal numbers (e.g., 3.14, -0.001)

age = 30        # integer
height = 1.75   # float

Strings

Text data, surrounded by single or double quotes.

message = "Hello, world!"

Booleans

Only two values: True or False (note the capital letters).

is_valid = True

3. Data Structures

Lists

Ordered, changeable collections.
Use square brackets [].

fruits = ["apple", "banana", "cherry"]

Tuples

Ordered, unchangeable collections.
Use parentheses ().

coordinates = (10, 20)

Dictionaries

Unordered collections of key-value pairs.
Use curly braces {}.

person = {"name": "Alice", "age": 30}

Sets

Unordered collections of unique items.
Use curly braces {} or the set() function.

unique_numbers = {1, 2, 3}

4. Common Pitfalls

Indentation Errors: Mixing tabs and spaces, or inconsistent indentation.
Case Sensitivity: Name and name are different variables.
Mutable vs. Immutable: Lists can be changed, but tuples cannot.
Using the Wrong Brackets: Lists use [], tuples use (), dictionaries use {}.

5. Summary Table

Data Type	Example	Mutable?
Integer	`x = 5`	No
Float	`y = 3.14`	No
String	`name = "Bob"`	No
Boolean	`flag = True`	No
List	`nums = [1, 2, 3]`	Yes
Tuple	`point = (1, 2)`	No
Dictionary	`d = {"a": 1}`	Yes
Set	`s = {1, 2, 3}`	Yes

6. Key Takeaways

Python’s syntax is simple but strict about indentation.
Understand the differences between data types and when to use each.
Be careful with mutable and immutable types.
Practice writing and reading code to reinforce these concepts.

This foundation will help you tackle more advanced coding problems and avoid common errors in Python.

Identifying Python Data Structures