FastAPI installation and setup - Step-by-Step Execution

Concept Flow - FastAPI installation and setup

Start

↓

Check Python installed

↓

Install FastAPI via pip

↓

Install ASGI server (uvicorn)

↓

Create main.py with FastAPI app

↓

Run uvicorn server

↓

Access API in browser or client

↓

End

This flow shows the steps to install FastAPI, set up a basic app, run the server, and access the API.

Execution Sample

FastAPI

pip install fastapi
pip install "uvicorn[standard]"

# main.py
from fastapi import FastAPI
app = FastAPI()

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

This code installs FastAPI and uvicorn, then creates a simple FastAPI app that returns a JSON greeting.

Execution Table

Step	Action	Command/Code	Result/Output
1	Check Python installed	python --version	Python 3.x.x (must be 3.7+)
2	Install FastAPI	pip install fastapi	FastAPI installed successfully
3	Install uvicorn server	pip install "uvicorn[standard]"	uvicorn installed successfully
4	Create main.py file	Write FastAPI app code	File main.py created with FastAPI app
5	Run uvicorn server	uvicorn main:app --reload	Server starts, listens on http://127.0.0.1:8000
6	Access API root	Open browser at http://127.0.0.1:8000/	Displays JSON: {"Hello": "World"}
7	Access docs	Open browser at http://127.0.0.1:8000/docs	Interactive API docs shown
8	Exit	Ctrl+C in terminal	Server stops

💡 User stops server manually with Ctrl+C

Variable Tracker

Variable	Start	After Step 4	After Step 5	Final
app	undefined	FastAPI instance created	Running FastAPI app instance	Running FastAPI app instance
server	not running	not running	uvicorn server running	server stopped

Key Moments - 3 Insights

Why do we need to install uvicorn separately after installing FastAPI?

FastAPI is the framework, but it needs an ASGI server like uvicorn to run the app and handle requests. See execution_table steps 2 and 3.

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

It makes the server restart automatically when you change your code, so you don't have to stop and start manually. See execution_table step 5.

How do we know the server is running and ready to accept requests?

The terminal shows the server address (http://127.0.0.1:8000) after running uvicorn. You can open this in a browser to see the response. See execution_table step 6.

Visual Quiz - 3 Questions

Look at the execution_table, what command installs the FastAPI framework?

A pip install uvicorn

B pip install fastapi

C uvicorn main:app --reload

D python main.py

💡 Hint

Check Step 2 in the execution_table for the FastAPI installation command.

At which step does the server start listening for requests?

A Step 5

B Step 6

C Step 4

D Step 7

💡 Hint

Look for the step where uvicorn is run and the server address appears.

If you forget to install uvicorn, what will happen when you try to run the server?

A The server will run normally

B FastAPI will install uvicorn automatically

C You will get an error saying uvicorn command not found

D The app will run but no requests will be handled

💡 Hint

Refer to the need for uvicorn in steps 3 and 5 of the execution_table.

Concept Snapshot

FastAPI installation and setup:
1. Ensure Python 3.7+ is installed.
2. Install FastAPI with 'pip install fastapi'.
3. Install uvicorn server with 'pip install "uvicorn[standard]"'.
4. Create a Python file with FastAPI app code.
5. Run server using 'uvicorn main:app --reload'.
6. Access API at http://127.0.0.1:8000/ in browser.

Full Transcript

To set up FastAPI, first check that Python 3.7 or newer is installed. Then, install FastAPI using pip. Next, install uvicorn, which is the server that runs the FastAPI app. Create a Python file named main.py with a FastAPI app instance and a simple route. Run the server with uvicorn using the command 'uvicorn main:app --reload'. The server will start and listen on http://127.0.0.1:8000/. You can open this URL in a browser to see the JSON response. The /docs path shows interactive API documentation. Stop the server anytime with Ctrl+C.

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