Python FastAPI: PyPI Introduction and Setup – wiki大全

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Python FastAPI: PyPI Introduction and Setup

Introduction to FastAPI

FastAPI is a modern, fast (high-performance) web framework for building APIs with Python 3.7+ based on standard Python type hints. It is designed to be easy to use, highly performant, and robust. Key features include:

  • Fast: Very high performance, on par with NodeJS and Go (thanks to Starlette and Pydantic).
  • Fast to code: Increase the speed to develop features by about 20% to 40%.
  • Fewer bugs: Decrease about 40% of human (developer) induced errors.
  • Intuitive: Great editor support. Completion everywhere. Less time debugging.
  • Easy: Designed to be easy to use and learn.
  • Short: Minimize code duplication. Multiple features from each parameter declaration.
  • Robust: Get production-ready code with automatic interactive documentation.
  • Standards-based: Based on (and fully compatible with) open standards for APIs: OpenAPI (previously Swagger) and JSON Schema.

FastAPI is built on top of Starlette for the web parts and Pydantic for the data parts.

What is PyPI?

PyPI, the Python Package Index, is the official third-party software repository for Python. It’s a vast collection of Python packages that developers can use to extend the functionality of their Python applications. When you use pip install some-package, pip (Python’s package installer) searches for “some-package” on PyPI, downloads it, and installs it into your Python environment.

PyPI serves several crucial roles in the Python ecosystem:

  • Distribution: It’s the primary channel for Python developers to share their libraries and applications with the wider community.
  • Discovery: Developers can easily find and learn about available packages through the PyPI website.
  • Dependency Management: It simplifies the process of managing project dependencies, ensuring that all necessary libraries are installed correctly.

Why use PyPI for FastAPI?

Using PyPI for FastAPI and its dependencies is the standard and most efficient way to manage your project. Here’s why:

  • Ease of Installation: pip install fastapi is all it takes to get started.
  • Dependency Resolution: PyPI and pip automatically handle installing FastAPI’s dependencies (like Starlette and Pydantic), ensuring compatibility.
  • Updates: Keeping your FastAPI version up-to-date is straightforward with pip install --upgrade fastapi.
  • Virtual Environments: PyPI packages integrate seamlessly with Python virtual environments, allowing you to isolate project dependencies and avoid conflicts.

FastAPI Installation and Setup

Let’s walk through the process of setting up a basic FastAPI project.

Prerequisites

  • Python 3.7+: Ensure you have a compatible Python version installed. You can check your version with python --version.

Creating a Virtual Environment

It’s highly recommended to use a virtual environment for every Python project. This isolates your project’s dependencies from other Python projects and your system-wide Python installation.

  1. Create a virtual environment:
    bash
    python -m venv venv
    (You can replace venv with your preferred environment name.)

  2. Activate the virtual environment:

    • On Windows:
      bash
      .\venv\Scripts\activate
    • On macOS/Linux:
      bash
      source venv/bin/activate
      Once activated, your terminal prompt will usually show (venv) indicating you’re in the virtual environment.

Installing FastAPI and Uvicorn

FastAPI itself is a framework, but it needs an ASGI (Asynchronous Server Gateway Interface) server to run. Uvicorn is a lightning-fast ASGI server, built on uvloop and httptools, and is commonly used with FastAPI.

bash
pip install fastapi "uvicorn[standard]"
The "[standard]" part for uvicorn includes additional optional dependencies for Uvicorn, which are generally useful.

Basic FastAPI Application

Create a file named main.py and add the following code:

“`python
from fastapi import FastAPI

app = FastAPI()

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

@app.get(“/items/{item_id}”)
async def read_item(item_id: int, q: str = None):
return {“item_id”: item_id, “q”: q}
“`

This simple application defines two endpoints:
* /: Returns a JSON response with “Hello, FastAPI!”.
* /items/{item_id}: Takes an integer item_id as a path parameter and an optional query parameter q.

Running the Application

With your virtual environment activated and dependencies installed, you can run your FastAPI application using Uvicorn:

bash
uvicorn main:app --reload

  • main: Refers to the main.py file.
  • app: Refers to the app object created inside main.py.
  • --reload: Tells Uvicorn to restart the server whenever code changes are detected, which is very useful during development.

You should see output similar to this:

INFO: Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
INFO: Started reloader process [xxxxx] using statreload
INFO: Started server process [yyyyy]
INFO: Waiting for application startup.
INFO: Application startup complete.

Now, open your web browser and navigate to http://127.0.0.1:8000. You should see {"message": "Hello, FastAPI!"}.

You can also visit http://127.0.0.1:8000/docs to see the automatic interactive API documentation provided by FastAPI (using Swagger UI), or http://127.0.0.1:8000/redoc for ReDoc documentation.

Conclusion

FastAPI, combined with the power of PyPI for package management, provides an incredibly efficient and enjoyable experience for building robust and high-performance APIs in Python. By following the standard setup process using virtual environments and pip, you can quickly get your projects up and running, leveraging FastAPI’s modern features and excellent developer experience.

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