Building an API with FastAPI
By the end of today you have a working API with several endpoints, and you can explain what the framework is doing for you at each point rather than treating it as magic.
YesterdayOn Day 35 you named the layers. Today you write them.
TomorrowTomorrow you harden the boundary, where untrusted input becomes trusted data.
Why this matters
Frameworks change; what they do does not. Understanding FastAPI as routing plus validation plus serialization means you can pick up Express, Django or anything else by asking the same questions.
- Web framework mechanics
- Where input arrives
- Dependency injection
- Seeing through the framework
Learn it
80 minCopy this into Claude or ChatGPT. It quizzes you before it explains anything, which is deliberate. The resources under it are how you check what it told you.
Today's Master Prompt
Free · sign inA prompt written for this day alone: your level, the exact scope, what to leave out, and an instruction to quiz you before it explains anything. Paste it into Claude or ChatGPT and it teaches you today's material.
Check it against something that is not a model
An assistant can be fluent and wrong, and on a topic you met today you will not catch it. These cover the same ground and were made by people who do this for a living, so they are what you hold the explanation up against. They are other people's work and we only link to them, so judge them for yourself.
5 hand-picked resources
Free · sign inVideos, official docs and articles covering the same ground, each opened and annotated by hand. They are what you check the assistant against on a day you cannot yet catch it being wrong.
Build it
50 minBuild a books API with all five operations, storing data in a dictionary. Use Pydantic models for both request and response, return the correct status code for each operation, and raise a proper 404 for a missing book. Then open the automatic docs and exercise every endpoint from there.
Recall it
20 minAnswer out loud, reveal, then mark honestly whether you had it. That score is the only thing on this page you do not get to choose.
5 recall questions
Free · sign inQuestions you answer from memory, then grade yourself against the real answer. The score is carried into the mastery rating below it, so an honest miss cannot quietly become a tick.
Rate it
Completion and mastery are tracked separately. Be honest, because an inflated rating only means the concept resurfaces sooner.
Mastery tracking
Free · sign inRate yourself against five named criteria per concept. Completion and mastery are tracked separately, and anything you rate shakily comes back automatically on a spaced schedule.
Recap
- 01A route decorator populates a lookup table at import time
- 02Pydantic validates at runtime, which annotations alone never do
- 03A response model stops internal fields leaking out
- 04Async helps only where something actually yields while waiting
Your progress
Free · sign inMark days complete, pick up where you left off across devices, and watch completion and mastery diverge. Free, and the account exists only so ninety days of work cannot vanish with a cleared browser.