python_snippets.md

Python

Hello World

print("Hello, World!")

Variables

name = "John"
age = 30

User Input

user_input = input("Enter something: ")

String Concatenation

first_name = "John"
last_name = "Doe"
full_name = first_name + " " + last_name

List Creation

my_list = [1, 2, 3, 4, 5]

List Slicing

subset = my_list[1:3]

List comprehension

squared_numbers = [x**2 for x in my_list]

Conditional Statements

if age > 18:
    print("You are an adult.")
elif age == 18:
    print("You are 18.")
else:
    print("You are under 18.")

For loop

for i in range(10):
    print(i)

While loop

count = 0
while count < 10:
    print(count)
    count += 1

Functions

def greet(name):
    return "Hello, " + name + "!"

File reading

with open("file.txt", "r") as file:
    content = file.read()

File writing

with open("output.txt", "w") as file:
    file.write("Hello, World!")

Exception handling

try:
    print(1/0)
except ZeroDivisionError:
    print("Cannot divide by zero.")

Dictionaries

my_dict = {
    "name": "John",
    "age": 30
}

Dictionary access

name = my_dict["name"]

Dictionary iteration

for key, value in my_dict.items():
    print(key, value)

Sets

my_set = {1, 2, 3, 4, 5}

Set operations

intersection = my_set.intersection({4, 5, 6})

Tuples

coordinates = (10, 20)

Lambda functions

square = lambda x: x**2

List Sorting

my_list.sort()

String Manipulation

my_string = "Hello, World!"
upper_text = my_string.upper()

List reversal

reversed_list = my_list[::-1]

Finding Maximum

max_value = max(my_list)

Finding Minimum

min_value = min(my_list)

List Length

length = len(my_list)

List removal

my_list.remove(3)

List Appending

my_list.append(6)

List copying

my_list_copy = my_list.copy()

List clearing

my_list.clear()

String Splitting

words = my_string.split(", ")

String Joining

my_string = ", ".join(words)

String Formatting

name = "John"
age = 30
my_string = f"Hello, my name is {name} and I am {age} years old."

Math Operations

result = abs(-5)

Random number generation

import random
random_number = random.randint(1, 10)

Date and Time

from datetime import datetime
current_time = datetime.now()

List unique values

unique_values = list(set(my_list))

Checking if a file exists

import os
if os.path.exists("file.txt"):
    print("File exists.")

Removing duplicates from a list

unique_values = list(dict.fromkeys(my_list))

List flattening

flat_list = [item for sublist in my_list for item in sublist]

List filtering

filtered_list = list(filter(lambda x: x > 5, my_list))

List mapping

mapped_list = list(map(lambda x: x**2, my_list))

List comprehension with condition

even_numbers = [x for x in range(10) if x % 2 == 0]

Using generators

def squares(n):
    for i in range(n):
        yield i**2

Handling JSON data

import json
data = {"name": "John", "age": 30}
json_data = json.dumps(data)

Reading JSON data

import json
with open("data.json", "r") as file:
    data = json.load(file)

Reading and writting CSV files

import csv

# Reading CSV
with open("data.csv", "r") as csvfile:
    reader = csv.DictReader(csvfile)
    for row in reader:
        print(row["name"], row["age"])

# Writing CSV
data = [{"name": "Alice", "age": 25}, {"name": "Bob", "age": 32}]
with open("output.csv", "w", newline="") as csvfile:
    fieldnames = ["name", "age"]
    writer = csv.DictWriter(csvfile, fieldnames=fieldnames)
    writer.writeheader()
    for row in data:
        writer.writerow(row)

Object-Oriented Programming (OOP)

class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def greet(self):
        return f"Hello, my name is {self.name}."

person = Person("Alice", 28)
print(person.greet())

Decorators

def log_function_call(func):
    def wrapper(*args, **kwargs):
        result = func(*args, **kwargs)
        print(f"Calling {func.__name__} with arguments {args} returned {result}.")
        return result
    return wrapper

@log_function_call
def add(a, b):
    return a + b

Threading

import threading

def print_numbers():
    for i in range(1, 6):
        print(f"Number {i}")

def print_letters():
    for letter in "abcde":
        print(f"Letter {letter}")

thread1 = threading.Thread(target=print_numbers)
thread2 = threading.Thread(target=print_letters)

Exception Handling with Custom Exceptions:

class CustomError(Exception):
    def __init__(self, message):
        super().__init__(message)

try:
    raise CustomError("This is a custom exception.")
except CustomError as e:
    print(e)

Working with Context Managers:

class MyContext:
    def __enter__(self):
        print("Entering the context")
        return self

    def __exit__(self, exc_type, exc_value, traceback):
        print("Exiting the context")

with MyContext() as context:
    print("Inside the context")

Multithreading with the concurrent.futures module:

import concurrent.futures

def square(x):
    return x**2

with concurrent.futures.ThreadPoolExecutor() as executor:
    results = executor.map(square, [1, 2, 3, 4, 5])

Working with Regular Expressions:

import re

pattern = r'\b\d{3}-\d{2}-\d{4}\b'
text = "My SSN is 123-45-6789."
match = re.search(pattern, text)

Sending Email with the smtplib module:

import smtplib
from email.mime.text import MIMEText

server = smtplib.SMTP("smtp.example.com")
msg = MIMEText("This is a test email.")
msg["Subject"] = "Test Email"
msg["From"] = "[email protected]"
msg["To"] = "[email protected]"
server.sendmail("[email protected]", "[email protected]", msg.as_string())
server.quit()

Working with REST APIs using the requests library

import requests

response = requests.get("https://jsonplaceholder.typicode.com/posts/1")
data = response.json()

Database Connection with sqlite3

import sqlite3

conn = sqlite3.connect("mydatabase.db")
cursor = conn.cursor()
cursor.execute("CREATE TABLE IF NOT EXISTS users (id INTEGER PRIMARY KEY, name TEXT, age INTEGER)")

Object Serialization with the pickle module

import pickle

data = {"name": "Alice", "age": 30}
with open("data.pickle", "wb") as file:
    pickle.dump(data, file)

Asynchronous Programming with asyncio

import asyncio

async def hello_world():
    await asyncio.sleep(1)
    print("Hello, World!")

asyncio.run(hello_world())

Working with Contextlib and the @contextmanager decorator

from contextlib import contextmanager

@contextmanager
def my_context():
    print("Entering the context")
    yield
    print("Exiting the context")

with my_context():
    print("Inside the context")

Working with bytes and Hexadecimal

data = b'Hello, World!'
hex_data = data.hex()

Using collections module

from collections import Counter

word_count = Counter(["apple", "banana", "apple", "cherry"])

Sending POST Request with the requests library

import requests

data = {"name": "Alice", "age": 25}
response = requests.post("https://example.com/api", json=data)