Python code explainers

python

from fastapi import APIRouter, Depends, Query
from pydantic import BaseModel
from sqlalchemy import func, select
from sqlalchemy.ext.asyncio import AsyncSession

How a paginated list endpoint works in FastAPI

pagination dependency-injection async-orm

Intermediate 8 steps

python

from fastapi import FastAPI, Request, status
from fastapi.responses import JSONResponse
 
app = FastAPI()

Custom exception handlers in FastAPI

exception handling error responses separation of concerns

Intermediate 7 steps

python

class FileManager:
    """A context manager that safely opens and closes a file."""
 
    def __init__(self, path, mode="r"):

Writing context managers in Python

context-managers resource-management exception-handling

Intermediate 6 steps

python

from collections import deque
 
 
def bfs(graph, start):

Breadth-first search and shortest paths in Python

graph-traversal bfs queue

Intermediate 9 steps

python

class Typed:
    """A data descriptor that enforces a type and optional validation."""
 
    def __init__(self, expected_type, validator=None):

Building a typed descriptor in Python

descriptors validation metaprogramming

Advanced 8 steps

python

from collections import Counter
 
 
def word_frequencies(text):

Counting things with collections.Counter

counting multiset data-structures

Beginner 8 steps

python

def two_sum_sorted(numbers, target):
    """Find indices of two values that sum to target in a sorted array."""
    left, right = 0, len(numbers) - 1
    while left < right:

Two-pointer search on sorted arrays

two-pointers arrays sorting

Intermediate 9 steps