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Programming Language

Python

Overview

Python is a general-purpose programming language with simple and readable syntax.

Details

Python is an interpreted programming language developed by Guido van Rossum in 1991, characterized by a design philosophy that emphasizes "code readability." With its rich standard library and vast third-party package ecosystem, Python is utilized across a wide range of fields from data analysis and machine learning to web development, desktop applications, and system administration. Its indentation-based block structure and simple grammar make it accessible to programming beginners while maintaining the flexibility to handle large-scale systems.

Code Examples

Hello World

# Basic output
print("Hello, World!")

# Output using variables
message = "Hello, Python!"
print(message)

# Output using format strings
name = "John"
age = 25
print(f"My name is {name} and I am {age} years old.")

File I/O

# Writing to a file
with open("sample.txt", "w", encoding="utf-8") as file:
    file.write("This is a test file.\n")
    file.write("Learning file operations in Python.")

# Reading from a file
with open("sample.txt", "r", encoding="utf-8") as file:
    content = file.read()
    print(content)

# Reading line by line
with open("sample.txt", "r", encoding="utf-8") as file:
    for line in file:
        print(line.strip())  # Remove newline characters

Conditional Statements

# Basic if statement
score = 85

if score >= 90:
    grade = "A"
elif score >= 80:
    grade = "B"
elif score >= 70:
    grade = "C"
else:
    grade = "D"

print(f"Score: {score}, Grade: {grade}")

# Combining multiple conditions
age = 20
has_license = True

if age >= 18 and has_license:
    print("You can drive")
elif age >= 18:
    print("Please get a license")
else:
    print("Please get a license after turning 18")

Lists, Dictionaries, Tuples

# List (array) operations
fruits = ["apple", "banana", "orange"]
fruits.append("grape")  # Adding an element
print(f"Fruit list: {fruits}")
print(f"First fruit: {fruits[0]}")

# Dictionary (hash) operations
person = {
    "name": "John Doe",
    "age": 30,
    "city": "Tokyo"
}
person["job"] = "Engineer"  # Adding new key-value pair
print(f"Name: {person['name']}, Age: {person['age']}")

# Tuple (immutable list)
coordinates = (10, 20)
print(f"Coordinates: x={coordinates[0]}, y={coordinates[1]}")

Loops and Iteration

# Processing list elements sequentially
numbers = [1, 2, 3, 4, 5]
for num in numbers:
    print(f"Number: {num}, Double: {num * 2}")

# Numeric loop using range()
for i in range(1, 6):
    print(f"Square of {i} is {i**2}")

# Processing dictionary elements
student_scores = {"John": 85, "Jane": 92, "Bob": 78}
for name, score in student_scores.items():
    print(f"{name}'s score: {score}")

# while loop
count = 0
while count < 5:
    print(f"Count: {count}")
    count += 1

Function Definition and Calling

# Basic function
def greet(name):
    """Function to greet someone"""
    return f"Hello, {name}!"

# Function with default arguments
def calculate_area(width, height=10):
    """Function to calculate rectangle area"""
    return width * height

# Function returning multiple values
def get_name_age():
    """Function to return name and age"""
    return "John Doe", 25

# Function calls
message = greet("Alice")
print(message)

area = calculate_area(5)  # height uses default value 10
print(f"Area: {area}")

name, age = get_name_age()  # Tuple unpacking
print(f"Name: {name}, Age: {age}")

Class Definition and Usage

class Car:
    """Class representing a car"""
    
    def __init__(self, make, model, year):
        """Constructor (initialization method)"""
        self.make = make      # Manufacturer
        self.model = model    # Model
        self.year = year      # Year
        self.mileage = 0      # Mileage
    
    def drive(self, distance):
        """Method to drive and increase mileage"""
        self.mileage += distance
        print(f"Drove {distance}km. Total mileage: {self.mileage}km")
    
    def get_info(self):
        """Method to get car information"""
        return f"{self.year} {self.make} {self.model}"

# Class instantiation and usage
my_car = Car("Toyota", "Prius", 2022)
print(my_car.get_info())
my_car.drive(50)
my_car.drive(30)

Library Usage

# Using standard libraries
import datetime
import random
import json

# Get current date and time
now = datetime.datetime.now()
print(f"Current time: {now.strftime('%Y-%m-%d %H:%M:%S')}")

# Generate random numbers
random_number = random.randint(1, 100)
print(f"Random number: {random_number}")

# JSON data processing
data = {
    "name": "Python Learner",
    "skills": ["basic syntax", "functions", "classes"],
    "level": "beginner"
}

# Convert dictionary to JSON string
json_string = json.dumps(data, indent=2)
print("JSON format:")
print(json_string)

# Example of popular third-party library
# Install with: pip install requests
try:
    import requests
    response = requests.get("https://api.github.com/users/python")
    if response.status_code == 200:
        user_data = response.json()
        print(f"GitHub user: {user_data['name']}")
except ImportError:
    print("requests library is not installed")

Special Features

List Comprehensions

# Basic list comprehension
squares = [x**2 for x in range(1, 6)]
print(f"Squares of 1-5: {squares}")

# Conditional list comprehension
even_squares = [x**2 for x in range(1, 11) if x % 2 == 0]
print(f"Even squares: {even_squares}")

Decorators

def timer(func):
    """Decorator to measure function execution time"""
    import time
    def wrapper(*args, **kwargs):
        start = time.time()
        result = func(*args, **kwargs)
        end = time.time()
        print(f"{func.__name__} execution time: {end - start:.4f}s")
        return result
    return wrapper

@timer
def slow_function():
    """Sample time-consuming process"""
    import time
    time.sleep(1)
    return "Processing complete"

result = slow_function()

Context Managers

class DatabaseConnection:
    """Example database connection context manager"""
    
    def __enter__(self):
        print("Connected to database")
        return self
    
    def __exit__(self, exc_type, exc_val, exc_tb):
        print("Database connection closed")
    
    def query(self, sql):
        print(f"Executing: {sql}")

# Safe resource management with with statement
with DatabaseConnection() as db:
    db.query("SELECT * FROM users")

Versions

Version Status LTS Release Date End of Support
Python 3.13 Latest - 2024-10-07 2029-10
Python 3.12 Current - 2023-10-02 2028-10
Python 3.11 Current - 2022-10-24 2027-10
Python 3.10 Current - 2021-10-04 2026-10
Python 3.9 Current - 2020-10-05 2025-10
Python 3.8 Security fixes only - 2019-10-14 2024-10
Python 2.7 End of life - 2010-07-03 2020-01-01

Reference Pages

Official Documentation

Learning Resources

Development Tools