Hand-picked tutorials, guides and examples on Programming Languages — explained simply.
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Rust is a compiled language that gives you C-level performance with memory safety guaranteed by the compiler, without a garbage collector. It powers parts of web browsers, operating systems, cloud infrastructure and a growing share of developer tooling. Where...
Go is a small, compiled language designed at Google for building reliable server software. Docker, Kubernetes, Terraform and many cloud tools are written in it. Its appeal is simplicity: a small language, fast builds, a single static binary and great built-in...
JavaScript gets a new edition every year. If you learned it a while ago, these additions will make your code shorter and safer. Safer property access const city = user?.address?.city; // undefined instead of a crash const limit = options.limit ?? 20; // only f...
Python 3.14 was released in October 2025. Here are the changes most developers will notice. Template strings (t-strings) A t-string looks like an f-string but produces a Template object instead of a finished string. Libraries can then process the interpolated...
Ownership is the idea that makes Rust memory-safe without a garbage collector. It comes down to three rules and two kinds of references. The three ownership rules Each value has exactly one owner (a variable). When the owner goes out of scope, the value is dro...
A goroutine is a lightweight thread managed by the Go runtime. You can run hundreds of thousands of them. Channels let goroutines pass data safely. Start goroutines and wait for them var wg sync.WaitGroup urls := []string{"https://go.dev", "https://pkg.go.dev"...
await in a loop runs requests one after another. JavaScript's promise combinators let you run them together and decide how to handle failures. Sequential vs parallel // Slow: each request waits for the previous one for (const id of ids) { results.push(await fe...
uv is a Python package and project manager written in Rust. It replaces pip, pip-tools, virtualenv, pyenv and pipx with one tool, and it's dramatically faster. Install curl -LsSf https://astral.sh/uv/install.sh | sh # or: pipx install uv, brew install uv Start...
Rust has no exceptions. Functions that can fail return Result<T, E> , and the compiler makes sure you deal with the error case. Result and match use std::fs; match fs::read_to_string("config.toml") { Ok(text) => println!("{} bytes", text.len()), Err(e) => epri...
In Go, errors are ordinary values returned alongside results. The pattern is repetitive by design: it keeps every failure path visible. The basic pattern f, err := os.Open("config.json") if err != nil { return fmt.Errorf("open config: %w", err) } defer f.Close...
sort() , reverse() and splice() change the original array. That causes subtle bugs, especially with React state, where you must not mutate. ES2023 added non-mutating versions. The old trap const scores = [30, 10, 20]; const ranked = scores.sort((a, b) => b - a...
Type hints don't change how Python runs, but editors and type checkers use them to catch bugs and power autocomplete. Modern Python syntax makes them short and readable. The basics def greet(name: str, times: int = 1) -> str: return ", ".join([f"Hello {name}"]...
Rust's enums are far more powerful than enums in most languages: each variant can hold its own data. Combined with match , they let you model states so that invalid ones can't exist. Structs and impl #[derive(Debug, Clone)] struct User { id: u64, name: String,...
Go developers used to reach for a router package as soon as they needed path parameters. Since Go 1.22, the standard http.ServeMux supports HTTP methods and wildcards, which covers most APIs. The server package main import ( "encoding/json" "log" "net/http" "s...
Grouping a list (orders by status, posts by month, people by team) used to need reduce or lodash. Object.groupBy does it in one line. Object.groupBy const orders = [ { id: 1, status: 'paid', total: 500 }, { id: 2, status: 'pending', total: 250 }, { id: 3, stat...
Both give you classes with typed fields and less boilerplate. The key difference: dataclasses store data, Pydantic validates and converts it. Dataclasses from dataclasses import dataclass, field @dataclass(frozen=True, slots=True) class Money: amount: int # pa...
A trait defines behaviour that types can implement, similar to an interface. Generics let functions work with any type that implements the traits they need. Defining and implementing a trait trait Notifier { fn send(&self, to: &str, message: &str) -> Result<()...
Generics arrived in Go 1.18. They let you write functions and types that work for many types while staying type-safe, without falling back to interface{} and type assertions. A generic function func Map[T, U any](items []T, fn func(T) U) []U { out := make([]U,...
JavaScript has had Set since ES2015, but combining sets meant converting to arrays and filtering. ES2025 added the classic set operations as methods. The operations const frontend = new Set(['asha', 'ravi', 'meera']); const oncall = new Set(['ravi', 'kiran']);...
asyncio lets one thread wait on many network operations at once. It shines for I/O-heavy work: calling APIs, scraping, chat servers, database queries. The basics import asyncio import httpx async def fetch_status(client: httpx.AsyncClient, url: str) -> int: re...
Async Rust lets one thread handle thousands of network connections. Rust provides async / await syntax; a runtime such as Tokio actually runs the futures. Setup [dependencies] tokio = { version = "1", features = ["full"] } reqwest = { version = "0.12", feature...
A context.Context carries a cancellation signal and an optional deadline through a chain of function calls. When a user closes the browser tab, every database query and HTTP call made for that request can stop. Every request already has one func handleSearch(w...
Array methods create a whole new array at each step. Iterator helpers work on iterators instead and are lazy : values are processed one at a time, only as many as you need. The methods iterator.map(fn) iterator.filter(fn) iterator.take(n) iterator.drop(n) iter...
match looks like a switch statement, but it's more powerful: it can check the shape of data and pull values out of it in one step. Literals and alternatives def http_message(status: int) -> str: match status: case 200 | 201: return "OK" case 404: return "Not f...
Axum is a popular Rust web framework from the Tokio team. Handlers are plain async functions, and "extractors" in their parameters pull data out of the request in a type-safe way. Dependencies [dependencies] axum = "0.8" tokio = { version = "1", features = ["f...
Go's testing tools are built in: no framework to choose. Tests live next to the code in _test.go files. Table-driven tests // slug_test.go func TestSlugify(t *testing.T) { tests := []struct { name, in, want string }{ {"simple", "Hello World", "hello-world"}, {...
Date mixes up dates, times and time zones, months start at 0, and objects are mutable. Temporal is a new built-in API that fixes these problems. It has started shipping in browsers; elsewhere you can use the official polyfill. npm install @js-temporal/polyfill...
pytest is the standard testing tool for Python. Tests are plain functions using plain assert , and pytest's output shows exactly what differed. First tests # test_pricing.py import pytest from pricing import apply_discount def test_ten_percent_discount(): asse...
Cargo is Rust's build tool and package manager. It's one of the best parts of the language, and a few features make a big difference in real projects. Everyday commands cargo new myapp # binary project (--lib for a library) cargo add serde --features derive ca...
A Go module is a collection of packages versioned together, defined by a go.mod file at its root. go.mod module github.com/acme/shop go 1.25 require ( github.com/jackc/pgx/v5 v5.7.1 golang.org/x/sync v0.10.0 ) Everyday commands go mod init github.com/acme/shop...
A closure is a function that remembers the variables from the place where it was created, even after that outer function has returned. Closures are behind callbacks, React hooks, module patterns and much more. Lexical scope const greeting = 'Hello'; function o...
Ruff is a Python linter and formatter written in Rust. It implements rules from Flake8 and many of its plugins, sorts imports like isort, and formats code in a Black-compatible style, typically in a fraction of a second. Install and run uv add --dev ruff uv ru...
Iterators are how idiomatic Rust processes collections. They read like a pipeline and compile down to code as fast as a hand-written loop. The basics let prices = vec![499, 1299, 250, 3999]; let affordable: Vec<u32> = prices .iter() // borrow each item .filter...
Since Go 1.23, for range can loop over functions . This gives Go a standard way to write iterators for custom data structures, database rows or paginated APIs. The iterator types // package iter type Seq[V any] func(yield func(V) bool) type Seq2[K, V any] func...
Some events fire very often: typing, scrolling, resizing. Running expensive work (an API call, a layout calculation) on every event wastes resources and can make the page janky. Debounce: wait until things calm down Run the function only after the events have...
A list holds every item in memory. A generator produces items one at a time, on demand. For large files, streams or infinite sequences, that's the difference between working and running out of memory. yield def read_lines(path): with open(path) as f: for line...
Rust evolves in small releases every six weeks, plus occasional editions that bundle changes which would otherwise break existing code. The 2024 edition shipped with Rust 1.85 in early 2025. Editions don't split the ecosystem Each crate picks its edition in Ca...
Plain text logs are hard to search at scale. Structured logs attach key-value fields to each message, so you can filter by user_id or status in your log platform. Go's standard library includes log/slog for this. Getting started import ( "log/slog" "os" ) func...
Users navigate away, type a new search or close a dialog while a request is still running. AbortController lets you cancel that work instead of letting it finish uselessly or, worse, overwrite newer results. Cancel a fetch const controller = new AbortControlle...
For decades, CPython's Global Interpreter Lock (GIL) allowed only one thread to run Python bytecode at a time. Threads helped with I/O, but not with CPU-heavy work. Free-threaded builds of Python remove the GIL. The timeline Python 3.13 introduced an experimen...
