Python Documentation

Introduction

Python is a high-level, interpreted programming language known for readable syntax and broad use across web development, automation, data science, and AI. Unlike compiled languages, Python code runs line-by-line through an interpreter, which makes it easier to test and debug quickly.

Python's design philosophy favors clarity — code is meant to read almost like plain English, which is part of why it's a common first language for beginners and a serious tool for professionals.

What You Should Already Know

Before starting, you should be comfortable with basic computer literacy — installing software, using a text editor, and navigating a file system. No prior programming experience is required, but understanding basic math operations (addition, comparison) will help.

Basic keyboard and file navigation skills
A text editor or IDE installed (e.g., VS Code)
Python installed and runnable from a terminal

Hello World

The traditional first program in any language prints a simple message to the screen. In Python, this takes one line, thanks to the built-in print() function.

print("Hello, world!")

Running this file through the Python interpreter outputs Hello, World! directly to the terminal.

Variables

A variable is a name that stores a value in memory, which you can reference and reuse. Python does not require you to declare a variable's type — it's inferred automatically from the value assigned.

                        name = "Ray"

                        age = 20

                        is_learning = True

Data Types

Python has several built-in data types that determine what kind of value a variable holds and what operations can be performed on it.

int — whole numbers (e.g., 10)
float — decimal numbers (e.g., 3.14)
str — text (e.g., "hello")
bool — True or False
list — an ordered, changeable collection

                        x = 10# int
                  
                        y = 3.14# float

                        name = "Ray"# str

                        is_ok = True# bool

Comparison Operators

Comparison operators compare two values and return a boolean (True or False). They're used constantly in control flow to test conditions.

                        a = 10

                        b = 5

                        print(a > b)# True

                        print(a == b)# False

                        print(a != b)# True

== equal to
!= not equal to
> < >= <= greater/less than (or equal)

Comments

Comments are lines in code that Python ignores when running the program. They exist purely to explain code to humans reading it — either yourself later, or others working on the same file.

                        # This is a single-line comment

                        print("This runs")# This explains the line

Control Flow

Control flow refers to the order in which a program's statements execute. Python uses if, elif, and else to make decisions based on conditions.

                        if x > 10:

                        print("Big")

                        elif x == 10:

                        print("Equal")

                        else:

                        print("Small")

Loops

Loops let you repeat a block of code multiple times without rewriting it. Python's most common loop, for, iterates over a sequence like a list or range of numbers.

                        for i in range(5):

                        print(i)

Functions

A function is a reusable block of code that performs a specific task, defined once and called whenever needed. Functions help avoid repeating code and make programs easier to organize and test.

                        def add(a, b):

                        return a + b

                        result = add(4, 6)

Data Structures

Data structures organize and store collections of related data. Python's two most-used built-in structures are lists (ordered collections) and dictionaries (key-value pairs).

Lists store ordered items, accessed by index: nums = [ 1, 2, 3]
Dictionaries store key-value pairs, accessed by key: person = { "name": "Ray"}

Choosing between them depends on whether you need to access data by position (list) or by a named label (dictionary).

File Handling

File handling lets a program read from or write to files stored on disk. Python's built-in open() function, used with, safely opens a file and automatically closes it afterward.

                        with open("file.txt") as f:

                        data = f.read()

                        print(data)

Opening a file in write mode ("w") instead of default read mode ("r") lets you save data to it.

Classes and OOP

Object-Oriented Programming (OOP) organizes code around objects — bundles of data (attributes) and behavior (methods) defined by a class, which acts as a blueprint.

                        class Student:

                        def __init__(self, name):

                        self.name = name

                        def greet(self):

                        print(f"Hi, I'm {self.name}")

                        s = Student("Ray")

                        s.greet()

class defines a blueprint for creating objects
__init__ runs automatically when an object is created, setting its initial attributes
self refers to the specific object calling the method