AI-assisted · Graded by real pytest

Solve. Run. Loop.

Interviews are AI-assisted now. FlowLoop teaches you to work with an AI pair programmer on realistic multi-file Python projects, then grades your solution with a real test suite instead of a single text box.

Start practicing for free Browse problems

Multi-file projectsReal pytest gradingAI pair programmer

Expense Ledger 12:48 · Implementation▶ Run Tests

EXPLORER
📁ledger/
📄parser.py
📄balance.py
📄__init__.py
📁tests/
📄test_parser.py🔒
📄test_balance.py🔒
parser.pybalance.py
1from .models import Entry
2
3def parse(line: str) -> Entry:
4# split "name,amount" into fields
5name, amount = line.split(",")
6return Entry(name, float(amount))
GuideAI AssistTests
Why does test_parser_negative fail?
Negative amounts start with a minus sign. float() handles it, so check that your split keeps the sign.
Latest run4/4 ✓

Multi-file projects •Real pytest grading •AI pair programmer •Guided walkthroughs •Voice answers •Progressive hints •Progress tracking •Sandbox mode •Multi-file projects •Real pytest grading •AI pair programmer •Guided walkthroughs •Voice answers •Progressive hints •Progress tracking •Sandbox mode •

How it works

Practice the full engineering loop

Every problem is a small codebase. You read it, fix it, and prove it works, the same way interviews actually run now.

Solve

Open a multi-file Python project in the browser IDE. Read the code, find the gaps, and make your changes with an AI pair programmer on call.

Run

Press Run and your code executes against the real pytest suite in a sandbox. You get per-test results, tracebacks, and the full output.

Loop

Use the feedback to iterate. Ask the AI sharper questions, reveal a hint, and fix the next failure. That loop is the skill interviews measure.

Guided walkthrough

An interview simulator that teaches as you go

Guided mode walks you through each problem phase by phase, like a good interviewer would. Explain your reasoning out loud or in writing and get instant, specific feedback. Then implement the fix and pass that phase's tests to unlock the next one.

Answer by voice or text and get specific, actionable feedback
Phase-scoped test runs keep you focused on one fix at a time
Progressive hints when you get stuck, always free
A full solution walkthrough when you finish

Try a guided interview

PHASE 2 OF 4 · EXPLAIN

234

Why does the parser drop negative amounts?

Walk through the bug the way you would for an interviewer, out loud or in writing.

Passed

Did well: Spotted that split(",") keeps the sign but float() never sees it.

To work on: Mention the failing test by name when you diagnose.

Continue to phase 3 →2 hints available

Everything in the loop

Built for how interviews work in the AI era

AI pair programmer

Chat with an assistant that sees the problem and your files. It coaches and reviews your work, but it never writes the solution for you.

Multi-file projects

Real package layouts with modules, models, and tests, because real work is never a single function in a text box.

Real test execution

Your code runs against canonical pytest suites in an isolated sandbox, so a passing run means your solution actually works.

Guided phases

Structured walkthroughs that alternate reasoning questions with focused coding steps.

Speak your answers

Practice explaining decisions out loud with in-browser voice input. That is the half of the interview most people never practice.

Progress that sticks

Workspaces autosave and phase progress is tracked, so you can leave mid-problem and pick up exactly where you stopped.

Your next interview will be AI-assisted.

Start with a free guided walkthrough. No credit card required, just a small codebase and a test suite to turn green.

Start your first problem