Python Basics

Overview

Python is a high-level, interpreted programming language known for its simplicity and readability. This document covers the basics of Python programming, including syntax, data types, and control structures.

Hello World

The classic first program in any language is to print "Hello, World!" to the console.

print("Hello, World!")

Variables and Data Types

Variables

Variables store data that can be used and manipulated in your programs.

x = 10
name = "Alice"

Example

age = 25
print(age)  # Output: 25

Data Types

Python supports several data types, including integers, floats, strings, and booleans.

• Integer: int
• Float: float
• String: str
• Boolean: bool

Example

integer_num = 10
float_num = 10.5
string_value = "Hello"
boolean_value = True

print(type(integer_num))  # Output: <class 'int'>
print(type(float_num))    # Output: <class 'float'>
print(type(string_value)) # Output: <class 'str'>
print(type(boolean_value))# Output: <class 'bool'>

Operators

Arithmetic Operators

• Addition: +
• Subtraction: -
• Multiplication: *
• Division: /
• Modulus: %
• Exponentiation: **
• Floor Division: //

Example

a = 10
b = 3

print(a + b)  # Output: 13
print(a - b)  # Output: 7
print(a * b)  # Output: 30
print(a / b)  # Output: 3.3333...
print(a % b)  # Output: 1
print(a ** b) # Output: 1000
print(a // b) # Output: 3

Comparison Operators

• Equal to: ==
• Not equal to: !=
• Greater than: >
• Less than: <
• Greater than or equal to: >=
• Less than or equal to: <=

Example

x = 10
y = 20

print(x == y)  # Output: False
print(x != y)  # Output: True
print(x > y)   # Output: False
print(x < y)   # Output: True
print(x >= y)  # Output: False
print(x <= y)  # Output: True

Control Structures

Conditional Statements

Use if, elif, and else for decision-making.

x = 10

if x > 0:
    print("x is positive")
elif x == 0:
    print("x is zero")
else:
    print("x is negative")

Example

number = 7

if number % 2 == 0:
    print("Even")
else:
    print("Odd")
# Output: Odd

Loops

for Loop

Iterate over a sequence (e.g., list, tuple, string).

for i in range(5):
    print(i)

Example

for i in [1, 2, 3, 4, 5]:
    print(i)
# Output:
# 1
# 2
# 3
# 4
# 5

while Loop

Repeat while a condition is true.

count = 0
while count < 5:
    print(count)
    count += 1

Example

num = 1
while num <= 5:
    print(num)
    num += 1
# Output:
# 1
# 2
# 3
# 4
# 5

Functions

Functions group reusable code. Use the def keyword to define a function.

def greet(name):
    return f"Hello, {name}!"

print(greet("Alice"))

Example

def add(x, y):
    return x + y

result = add(10, 5)
print(result)  # Output: 15

Lists

Lists store multiple items in a single variable. Lists are ordered and mutable.

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

Example

numbers = [1, 2, 3, 4, 5]
print(numbers[0])  # Output: 1
print(numbers[1:3])# Output: [2, 3]

Dictionaries

Dictionaries store key-value pairs. They are unordered and mutable.

person = {"name": "Alice", "age": 25}

Example

student = {"name": "John", "grade": "A"}
print(student["name"])  # Output: John

Summary

This document covers fundamental Python concepts, including variables, data types, operators, control structures, functions, lists, and dictionaries. Python’s simplicity and readability make it a great choice for both beginners and experienced developers. For more in-depth information, refer to the official Python documentation.