DEV Community: Hyunjung

How to start FastAPI?

Hyunjung — Sun, 12 Apr 2026 10:47:45 +0000

I’m starting a new FastAPI project for my capstone, and I want to document the entire process so I can look back on it later.

Prerequisites

Python 3.10+ installed
Git installed and configured
A GitHub account
Basic terminal knowledge

1. Create your project folder

mkdir my-project
cd my-project

2. Set up a virtual environment

Always use a virtual environment.

python -m venv venv

Activate it:

# macOS / Linux
source venv/bin/activate

# Windows (CMD)
venv\Scripts\activate.bat

Your terminal prompt should now show (venv) at the start.

3. Install FastAPI and Uvicorn

pip install fastapi uvicorn

uvicorn is the ASGI server that runs your FastAPI app.

4. Freeze your dependencies

pip freeze > requirements.txt

This creates a requirements.txt file so anyone can reproduce your environment with:

pip install -r requirements.txt

5. Create your first app

Create a file called main.py at the root of your project:

from fastapi import FastAPI

app = FastAPI()

@app.get("/")
def read_root():
    return {"message": "Hello, FastAPI!"}

6. Run the dev server

uvicorn main:app --reload

Now open your browser and visit:

http://127.0.0.1:8000 — your root endpoint
http://127.0.0.1:8000/docs — auto-generated Swagger UI

FastAPI auto-generates interactive API docs from your code.

7. Structure your project (optional but recommended)

For a capstone or real project, a flat main.py will get messy fast. Here's a minimal structure that scales well:

my-fastapi-project/
├── app/
│   ├── __init__.py
│   ├── main.py
│   └── models/
│       ├── __init__.py
├── requirements.txt
├── .gitignore
└── README.md

Update your entry point to point to app.main:

uvicorn app.main:app --reload

8. Add a .gitignore

Before committing anything, create a .gitignore so you don't accidentally push your virtual environment or secrets:
you can get text from gitignore.io

9. Write a README.md

just as you want~

10. Initialize Git and push to GitHub

Create a repo on GitHub
Connect and push

This is really easy and you can do it.

Done! Your FastAPI project is now on GitHub.

React Native App Development: Error I solved(2)

Hyunjung — Tue, 17 Mar 2026 15:09:30 +0000

1. Install NDK

To implement screen navigation, I installed react-native-screens along with other related packages. However, I ran into a build error during the process.

The root cause was that Android requires the NDK (Native Development Kit) to execute native code. Without a properly configured NDK, some native modules fail to build.

After installing an NDK version compatible with my Gradle setup, the issue with react-native-screens was successfully resolved.

2. Edit Environment Variables

While downloading various packages and editing environment variables for my React Native project, I accidentally modified some user variables that were already set.

After saving the changes, I couldn’t remember the original paths. As a result, I had to manually locate each one and restore them.

3. Error in MainActivity

While fixing some errors, I learned that I needed to modify MainActivity. I made the changes and tried to build the project again, but it failed.

I realized I had made a mistake in the code, so I got help from Google and ChatGPT. After correcting the issue, I was able to implement a MainActivity that worked properly.

package com.myreact

import android.os.Bundle
import com.facebook.react.ReactActivity
import com.facebook.react.ReactActivityDelegate
import com.facebook.react.defaults.DefaultNewArchitectureEntryPoint.fabricEnabled
import com.facebook.react.defaults.DefaultReactActivityDelegate

class MainActivity : ReactActivity() {
    /**
     * Returns the name of the main component registered from JavaScript. This is used to schedule
     * rendering of the component.
     */
    override fun getMainComponentName(): String = "MyReact"

    /**
     * Returns the instance of the [ReactActivityDelegate]. We use [DefaultReactActivityDelegate]
     * which allows you to enable New Architecture with a single boolean flags [fabricEnabled]
     */
    override fun createReactActivityDelegate(): ReactActivityDelegate =
        DefaultReactActivityDelegate(this, mainComponentName, fabricEnabled)

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
    }
}

4. Installed the Gesture Handler Package (this is not error!)

React Native App Development: Errors I Solved (1)

Hyunjung — Mon, 16 Mar 2026 14:22:57 +0000

React Native requires installing many packages, so versions are very important. Here are some issues I encountered and how I solved them while developing my app:

1. Java version must be 17
I made sure my Java version matched the one required by my current project.

2. Reinstall React Native
Sometimes builds would fail during development. After some searching, I found that uninstalling and reinstalling react-native-cli and react-native often solves the issue:

   npm uninstall -g react-native-cli
   npm uninstall -g react-native
   npm install -g react-native-cli
   npm install -g react-native

3. Fixing react-native-community/cli errors
I ran into an error related to react-native-community/cli, so I removed it from my system.

4. Create a new project
After resolving the above issues, I created a new React Native project:

   npx react-native init MyReact

5. Gradle error
Initially, everything seemed fine, but I ran into Gradle errors. Some suggested downgrading Gradle from 8.6 to 8.5, but that didn’t fix it.
It turned out the problem was with Android Studio. The error mentioned it couldn’t find the Gradle from another project I wasn’t currently working on.
The solution was to open my current app project in Android Studio and run it once. After that, building with React Native worked perfectly.