CentOS 9用户必看：GitHub明星项目Flask详解

引言

Flask是一个轻量级的Python Web框架，因其简洁、灵活的特性在GitHub上获得了超过65k的星标。本文将带领CentOS 9用户从零开始搭建Flask开发环境，并通过一个完整的示例项目展示其核心功能。

准备工作

环境要求

CentOS 9操作系统
Python 3.9或更高版本
pip包管理工具
基础的Linux命令行知识

检查当前环境

代码片段

# 检查系统版本
cat /etc/centos-release

# 检查Python版本
python3 --version

# 检查pip版本
pip3 --version

安装步骤

1. 安装Python和必要工具

代码片段

# CentOS默认可能没有安装Python3，先安装它
sudo dnf install python3 python3-pip python3-devel -y

# 安装开发工具组（包含gcc等编译工具）
sudo dnf groupinstall "Development Tools" -y

# 验证安装
python3 --version && pip3 --version

注意事项：
– CentOS默认的Python2已被淘汰，务必使用Python3
– python3-devel包含开发Flask扩展可能需要的头文件

2. 创建虚拟环境

代码片段

# 安装虚拟环境工具
sudo pip3 install virtualenv

# 创建项目目录并进入
mkdir flask_project && cd flask_project

# 创建虚拟环境（命名为venv）
python3 -m virtualenv venv

# 激活虚拟环境
source venv/bin/activate

# (激活后提示符前会出现(venv)标记)

原理说明：
虚拟环境可以隔离项目依赖，避免不同项目间的包冲突。激活后所有pip安装的包都会安装在当前环境的venv目录下。

3. 安装Flask及相关扩展

代码片段

(venv) pip install flask flask-sqlalchemy flask-wtf flask-login

# 验证安装成功
(venv) python -c "import flask; print(flask.__version__)"

常用扩展说明：
– flask-sqlalchemy: ORM数据库支持
– flask-wtf: Web表单处理
– flask-login: 用户认证管理

Flask基础示例：构建一个博客应用

1. 项目结构创建

代码片段

(venv) mkdir -p app/{templates,static} 
(venv) touch app/__init__.py app/routes.py app/models.py app/forms.py config.py run.py

最终目录结构：

代码片段

flask_project/
├── venv/
├── app/
│   ├── __init__.py       # Flask应用工厂函数
│   ├── routes.py         # URL路由定义 
│   ├── models.py         # 数据模型定义  
│   ├── forms.py          # Web表单定义  
│   ├── templates/        # HTML模板  
│   └── static/           # CSS/JS静态文件  
├── config.py             # 配置文件  
└── run.py                # 启动脚本

2. Flask应用初始化代码

编辑app/__init__.py:

代码片段

from flask import Flask 
from config import Config 

def create_app(config_class=Config):
    """应用工厂函数"""
    app = Flask(__name__)
    app.config.from_object(config_class)

    # TODO:后续添加数据库和扩展初始化

    return app

编辑config.py:

代码片段

import os 

class Config:
    SECRET_KEY = os.environ.get('SECRET_KEY') or 'your-secret-key-here'
    SQLALCHEMY_DATABASE_URI = 'sqlite:///' + os.path.join(os.path.dirname(__file__), 'app.db')
    SQLALCHEMY_TRACK_MODIFICATIONS = False

3. Hello World路由示例

编辑app/routes.py:

代码片段

from flask import render_template 
from app import create_app 

app = create_app()

@app.route('/')
@app.route('/index')
def index():
    return render_template('index.html', title='Home')

@app.route('/hello/<name>')
def hello(name):
    return f'Hello, {name}!'

创建模板文件app/templates/index.html:

代码片段

<!DOCTYPE html>
<html>
<head>
    <title>{{ title }}</title>
</head>
<body>
    <h1>Welcome to My Flask Blog!</h1>
</body>
</html>

4. SQLAlchemy模型示例（可选）

编辑app/models.py:

代码片段

from datetime import datetime 
from app import db 

class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(64), index=True, unique=True)
    email = db.Column(db.String(120), index=True, unique=True)
    posts = db.relationship('Post', backref='author', lazy='dynamic')

class Post(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    body = db.Column(db.String(140))
    timestamp = db.Column(db.DateTime, index=True, default=datetime.utcnow)
    user_id = db.Column(db.Integer, db.ForeignKey('user.id'))

更新__init__.py初始化数据库：

“`python {5-6,11}
from flask import Flask
from config import Config
from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()

def createapp(configclass=Config):
app = Flask(name)
app.config.fromobject(configclass)

代码片段

db.init_app(app)

return app

代码片段


### 5. WSGI启动文件（生产部署）

创建`wsgi.py`：

from app import create_app 

app = create_app()

if __name__ == '__main__':
    app.run()

Flask应用运行与测试

开发模式运行：

代码片段

(venv) export FLASK_APP=run.py FLASK_ENV=development 
(venv) flask run --host=0.0.0.0 --port=5000

访问测试：
1. http://localhost:5000
2. http://localhost:5000/hello/world

Gunicorn生产部署：

“`bash {2}
(venv) pip install gunicorn
(venv) gunicorn -w4 -b127.0.0.1:8000 wsgi:app

-w4: worker数量为4个CPU核心数

wsgi:app表示从wsgi模块加载app对象

代码片段


## CentOS特定问题解决指南

1. **SELinux阻止端口访问**
   ```bash {2}
   sudo dnf install policycoreutils-python-utils -y 
   sudo semanage port -a -t http_port_t -p tcp5000

防火墙配置
“`bash {2}
sudo firewall-cmd –permanent –add-port=5000/tcp
sudo firewall-cmd –reload

代码片段


3. **Python模块找不到问题**
   ```bash {2}
   #如果出现ImportError，尝试重新链接库文件:
   sudo ln -s /usr/local/lib/pythonX.Y/site-packages/path_to_module /usr/lib/pythonX.Y/site-packages/

Flask最佳实践建议

项目结构组织

代码片段

myproject/
  ├── requirements.txt      #依赖列表  
  ├── instance/            #实例文件夹（存放敏感配置）  
  ├── migrations/           #数据库迁移脚本  
  └── tests/               #单元测试目录

生产环境配置
python {4} class ProductionConfig(Config): DEBUG = False SECRET_KEY = os.environ.get('SECRET_KEY') or 'prod-secret-key' SQLALCHEMY_DATABASE_URI = os.environ.get('DATABASE_URL') or \ 'postgresql://user:password@localhost/mydatabase'

Flask生态推荐扩展清单

扩展名称	用途	安装命令
Flask-RESTful	构建REST API	pip install flask-restful
Flask-Migrate	数据库迁移	pip install flask-migrate
Flask-Caching	缓存支持	pip install flask-caching
Flask-Mail	邮件发送	pip install flask-mail

Git版本控制集成（可选）

“`bash {2} {5}
git init .
echo “venv/” > .gitignore

git add .
git commit -m “Initial commit with basic Flask structure”
git remote add origin https://github.com/YOURUSER/flask-project.git
git push -u origin main

代码片段


## Web服务器部署(Nginx + Gunicorn)

1. **Nginx配置示例**:
   ```nginx {6} {8} {10} {12}
   server {
       listen80;
       server_name yourdomain.com;

       location / {
           proxy_pass http://127.0.0.1:8000;
           proxy_set_header Host $host;
           proxy_set_header X-Real-IP $remote_addr;
           proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
       }

       location /static {
           alias /path/to/flask_project/app/static;
       }

       error_log /var/log/nginx/flask_error.log;access_log /var/log/nginx/flask_access.log;

       client_max_body_size20M;client_body_buffer_size128k;

       keepalive_timeout65;keepalive_requests100;send_timeout75s;

       gzipon;gzip_types text/css application/javascript application/json image/svg+xml text/xml application/xml+rss text/javascript;

       if ($request_method !~ ^(GET|HEAD|POST)$ ){return405;}

       add_header X-Frame-Options SAMEORIGIN always;add_header X-XSS-Protection "1; mode=block" always;add_header X-Content-Type-Options nosniff always;add_header Referrer-Policy strict-origin-when-cross-origin always;add_header Content-Security-Policy "default-src 'self'; script-src 'self' 'unsafe-inline' cdn.example.com; style-src 'self' 'unsafe-inline' cdn.example.com; img-src 'self' data: cdn.example.com;" always;

       ssl_certificate /etc/letsencrypt/live/yourdomain.com/fullchain.pem;ssl_certificate_key /etc/letsencrypt/live/yourdomain.com/privkey.pem;ssl_protocols TLSv1 TLSv1 .TLS v.TLS v.;ssl_prefer_server_cipherson ;ssl_ciphers EECDH+AESGCM : EDH+AESGCM : AES+EECDH : AES+EDH ;ssl_ecdh_curve secp r ;ssl_session_cache shared : SSL : m ;ssl_session_tickets off ;ssl_stapling on ;ssl_stapling_verify on ;resolver8..4..48.. valid=300s ;resolver_timeout5s ;




















}

server {
listen443 ssl http ;
server_name yourdomain.com ;
include snippets / ssl-yourdomain.com.conf ;
include snippets / security-headers.conf ;

location / {
proxy_pass http : //127...800 ;
proxy_set_header Host $host ;
proxy_set_header X Real IP $remote_addr ;
proxy_set_header X Forwarded For $proxy_add_x_forwarded_for ;
}

location ~ /.well known {
allow all ;
}

error_page404404.html ;error_page50050250350450x.html ;

access_log off ;log_not_found off ;

}

}

“`
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