Fastapi Tutorial – Complete Guide

Welcome to our comprehensive tutorial on FastAPI, a high-performance, easy-to-learn Python web framework. As we delve into the world of coding and building dynamic APIs, we invite learners of all levels to join us on this exciting journey!

So, What Exactly is FastAPI?

FastAPI is a modern, fast (high-performance), web framework for building APIs with Python 3.6+ based on standard Python type hints.

The key purpose of FastAPI is to enable developers to create robust APIs quickly and with fewer bugs. It provides a concise, user-friendly platform to code in Python. It’s primarily used when building high-performance applications due to its speed and efficiency.

Why Learn FastAPI?

If you’re wondering why you should invest your time in learning FastAPI, consider the following benefits:

  • With FastAPI, you get an incredibly fast framework, on par with NodeJS and Go.
  • It leads to less debugging due to its easy error handling.
  • It offers an interactive API documentation, ensuring you have fewer doubts while coding.
  • Lastly, learning FastAPI opens up new job opportunities as the demand for FastAPI developers is high in the tech industry.

FastAPI equips you with tools and knowledge that can set you apart in your coding journey. It’s a valuable addition to your repertoire, and with us here at Zenva, learning it will be an exciting adventure!

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Getting Started with FastAPI

FastAPI, like any Python framework, requires installation. Let’s start by installing it in your development environment.

(Create a virtual environment and activate it before installing FastAPI)

pip install fastapi

Then, install Uvicorn, an ASGI server, to enable your application to run.

pip install uvicorn

Now that we have FastAPI and Uvicorn installed, let’s start creating our first API with FastAPI.

Creating Your First API with FastAPI

In your editor, create a new Python file and import FastAPI.

from fastapi import FastAPI

app = FastAPI()

def read_root():
    return {"message": "Hello, world!"}

In this example, we create an instance of FastAPI. We then create an endpoint at root (“/”) which will return a JSON response when accessed using a GET request.

Running Your FastAPI Application

You can run FastAPI applications with Uvicorn. In your terminal, use the command:

uvicorn main:app --reload

On navigating to localhost at port 8000 in your browser, you should see your “Hello, world!” message.

Creating API Endpoints

You can create more endpoints by adding more route functions.

def read_item(item_id: int):
    return {"item_id": item_id}

In this example, “/items/{item_id}” is a path with a path parameter of item_id. The item_id in the function parameters is automatically validated and converted to an integer.

FastAPI makes creating APIs straightforward and efficient, qualities that are highly valued in web development today. In the next part, we will cover more advanced concepts and further showcase the flexibility and power of FastAPI.

Query Parameters

FastAPI allows for easy handling of query parameters. Let’s consider an example where we have an optional query parameter:

from typing import Optional

def read_items(q: Optional[str] = None):
    return {"query": q}

Here, the function will return the query parameter q. If q is not provided in the URL, it will default to None.

Request Body

FastAPI provides support for parsing request bodies using Pydantic models. Let’s start by defining a Pydantic model:

from pydantic import BaseModel

class Item(BaseModel):
    name: str
    description: Optional[str] = None
    price: float
    tax: Optional[float] = None

Now, we can use this model in our route:"/items/")
def create_item(item: Item):
    return item

This tells FastAPI that the request body for this POST route is modeled by the Item class.


FastAPI can also parse headers. Headers are defined as function parameters using Python’s title case string conventions. Here’s an example:

def read_items(user_agent: Optional[str] = Header(None)):
    return {"User-Agent": user_agent}

In this case, FastAPI will capture the “User-Agent” from the headers into the user_agent parameter.

HTTP Cookies and Sessions

FastAPI has built-in support for cookies and sessions. Here’s an example of FastAPI using cookies:

def read_items(session_token: Optional[str] = Cookie(None)):
    return {"session_token": session_token}

If the request contains a cookie named session_token, it will capture it into the session_token variable.

FastAPI provides a wealth of functionality that allows developers to build robust APIs with fewer bugs and an increased development speed. In our next section, we will delve into deeper concepts, further showcasing the flexibility and power of FastAPI.

Where to Go Next?

As you continue your coding journey, you’ll soon realize the depths you can reach and the creative and practical applications you can achieve. There’s so much you can learn and explore further. Notably among them is the world of Python programming, and we’ve got the perfect guide for you: our Python Mini-Degree.

Our Python Mini-Degree is a comprehensive collection of courses that span from Python programming basics to advanced concepts. It’s a perfect mix of theoretical learning and hands-on experience designed for beginners, and for experienced learners desiring to refine their skills. The courses include a wide range of exciting projects such as creating arcade games, a medical diagnosis bot, an escape room, and more.

Python is the most favored programming language globally and in high demand in the job market, especially in data science. Our Python Mini-Degree, hence, not only boosts your programming skills but also amplifies your career prospects.

Here’s why you should consider our Mini-Degree program:

  • Courses are flexible and accessible 24/7, letting you learn at your own pace.
  • Zenva provides engaging learning experiences through quick challenges and in-course quizzes.
  • Experienced, Unity Technologies and CompTIA certified instructors lead you.
  • Get to build a portfolio of Python projects and learn skills that can apply across industries.
  • Courses are regularly updated to align with industry practices.

For intermediate learners, we also have a variety of Python courses tailored to suit your needs. You can check them out here.

Your journey to becoming a professional programmer is a marathon, not a sprint. So, keep learning and keep growing with us, here at Zenva. The world of programming welcomes you with unlimited possibilities and opportunities. Happy coding!


FastAPI is a versatile web framework that helps developers build APIs rapidly while ensuring high performance and fewer bugs. This makes it a valuable skill to have in your developer toolkit. However, remember that the journey to mastering programming doesn’t end with learning a single framework. There’s an exciting world of Python programming awaiting your exploration.

So, why wait? Take the leap and advance your coding journey with our Python Mini-Degree. Gain hands-on experience working on real-world projects and unlock a world of opportunities. We are here at Zenva, committed to nurturing talents like you, turning programming enthusiasts into industry-ready professionals. So, let’s keep learning, keep coding, and reach new heights together!

Did you come across any errors in this tutorial? Please let us know by completing this form and we’ll look into it!

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