FastAPI installation and setup - Cheat Sheet & Quick Revision

Recall & Review

beginner

What command do you use to install FastAPI?

You use pip install fastapi to install FastAPI.

beginner

Why do you also need to install an ASGI server like Uvicorn when using FastAPI?

FastAPI is a framework, but it needs an ASGI server like Uvicorn to run your app and handle web requests.

beginner

What is the command to install Uvicorn with recommended extras?

You run pip install "uvicorn[standard]" to install Uvicorn with useful extras for production.

beginner

How do you start a FastAPI app using Uvicorn from the command line?

Use uvicorn main:app --reload where main is your Python file and app is your FastAPI instance. The --reload option restarts the server on code changes.

beginner

What is the minimal FastAPI app code to test your setup?

```python
from fastapi import FastAPI
app = FastAPI()

@app.get("/")
async def read_root():
    return {"Hello": "World"}
```

Which command installs FastAPI?

A pip install uvicorn

B pip install flask

C pip install fastapi

D pip install django

FastAPI is installed using pip install fastapi.

What role does Uvicorn play in FastAPI setup?

A It is an ASGI server to run the app

B It is a database

C It is a frontend framework

D It is a testing tool

Uvicorn is an ASGI server that runs FastAPI apps and handles web requests.

What does the --reload option do when running Uvicorn?

A Restarts server on code changes

B Enables debugging mode

C Runs server in production mode

D Disables logging

The --reload option restarts the server automatically when you change your code.

Which file and variable do you specify to run a FastAPI app with Uvicorn?

A server.py:fastapi

B app.py:main

C filename:app

D main:app

You specify main:app where main.py is the file and app is the FastAPI instance.

What is the first step after installing FastAPI and Uvicorn to see your app running?

A Install a database

B Write a FastAPI app code

C Run <code>python main.py</code>

D Open a browser

You need to write a FastAPI app code before running it with Uvicorn.

Describe the steps to install and run a basic FastAPI app.

Think about installation, coding, and running the server.

Explain why you need both FastAPI and Uvicorn to run a web app.

One builds, the other runs.

Practice

1. What is the main command to install FastAPI with all optional dependencies for full functionality?

easy

A. pip install fastapi[all]

B. pip install fastapi-core

C. pip install fastapi-full

D. pip install fastapi-basic

Solution

1. Step 1: Understand FastAPI installation options

   FastAPI can be installed with or without optional dependencies. The command with [all] installs everything needed for full features.

2. Step 2: Identify the correct pip command

   The correct command to install FastAPI with all optional dependencies is pip install fastapi[all].

3. Final Answer:

   pip install fastapi[all] -> Option A

4. Quick Check:

   Full install command = pip install fastapi[all] [OK]

Hint: Remember: [all] installs everything FastAPI needs [OK]

Common Mistakes:

• Using pip install fastapi without [all] misses optional tools
• Trying pip install fastapi-core which doesn't exist
• Confusing with pip install fastapi-full or fastapi-basic

2. Which command correctly runs a FastAPI app locally using Uvicorn?

easy

A. uvicorn app:app --reload

B. fastapi run app.py

C. python app.py

D. uvicorn run app.py

Solution

1. Step 1: Identify the tool to run FastAPI apps

   Uvicorn is the ASGI server used to run FastAPI apps locally for testing.

2. Step 2: Use the correct command syntax

   The correct command is uvicorn app:app --reload, where the first 'app' is the Python file name (without .py) and the second 'app' is the FastAPI instance.

3. Final Answer:

   uvicorn app:app --reload -> Option A

4. Quick Check:

   Run FastAPI with uvicorn app:app --reload [OK]

Hint: Use uvicorn with file:instance and --reload for dev [OK]

Common Mistakes:

• Trying to run FastAPI with python app.py directly
• Using wrong uvicorn syntax like 'uvicorn run app.py'
• Confusing fastapi run command which does not exist

3. Given this command run in terminal: uvicorn main:app --reload, what does the --reload flag do?

medium

A. Disables debugging features

B. Automatically restarts the server on code changes

C. Runs the server in production mode

D. Compiles the app to bytecode

Solution

1. Step 1: Understand the purpose of --reload flag

   The --reload flag tells Uvicorn to watch for code changes and restart the server automatically.

2. Step 2: Identify what happens without --reload

   Without --reload, the server runs but does not restart on code edits, making development slower.

3. Final Answer:

   Automatically restarts the server on code changes -> Option B

4. Quick Check:

   --reload means auto restart on code change [OK]

Hint: Reload flag = auto restart server on code edits [OK]

Common Mistakes:

• Thinking --reload enables production mode
• Assuming it disables debugging
• Believing it compiles code instead of reloading

4. You run uvicorn app:app --reload but get an error: ModuleNotFoundError: No module named 'app'. What is the likely cause?

medium

A. Uvicorn is not installed

B. The FastAPI instance is not named 'app' inside the file

C. The Python file named app.py does not exist in the current directory

D. The --reload flag is incompatible with your Python version

Solution

1. Step 1: Understand the error meaning

   The error means Python cannot find a module named 'app', which should be the filename without .py.

2. Step 2: Check the file existence

   If the file app.py is missing or you are in the wrong directory, this error occurs.

3. Final Answer:

   The Python file named app.py does not exist in the current directory -> Option C

4. Quick Check:

   ModuleNotFoundError means missing file/module [OK]

Hint: Check your file name and directory for the module [OK]

Common Mistakes:

• Assuming Uvicorn is not installed causes this error
• Thinking the FastAPI instance name causes ModuleNotFoundError
• Blaming --reload flag for import errors

5. You want to start a new FastAPI project. Which sequence correctly sets up and runs your app locally?

hard

A. pip install fastapi[all] -> create app.py -> uvicorn run app.py

B. pip install uvicorn -> create app.py -> python app.py

C. pip install fastapi -> create app.py -> fastapi run app.py

D. pip install fastapi[all] -> create app.py with FastAPI instance -> uvicorn app:app --reload

Solution

1. Step 1: Install FastAPI with all dependencies

   Use pip install fastapi[all] to get FastAPI and recommended tools like Uvicorn.

2. Step 2: Create your app.py file with a FastAPI instance named 'app'

   This file contains your API code and the FastAPI() instance.

3. Step 3: Run the app locally with Uvicorn and reload

   Use uvicorn app:app --reload to start the server with auto-reload for development.

4. Final Answer:

   pip install fastapi[all] -> create app.py with FastAPI instance -> uvicorn app:app --reload -> Option D

5. Quick Check:

   Install, create app, run with uvicorn --reload [OK]

Hint: Install FastAPI[all], create app.py, run uvicorn app:app --reload [OK]

Common Mistakes:

• Installing only uvicorn without FastAPI
• Trying to run app.py directly with python
• Using wrong uvicorn command syntax