Python Flask微框架入门与部署实践

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"Learning Flask" 是一篇关于Python轻量级Web应用框架Flask的教程。Flask是基于Werkzeug库构建的，尽管被称为“微型”，但它已经具备了在各种场景下进行生产级应用的能力。本文将逐步介绍如何入门Flask，包括安装、配置和关键功能。 **第1章：Flask入门** - 这部分会引导读者快速开始Flask项目，首先讲解稳定版和最新版的安装方法，以及如Sphinx文档生成工具和测试框架如py.test和tox的集成。 **第2章：访问请求数据** - 在这一章节，读者将学习如何处理HTTP请求，包括查询字符串、表单数据的获取和管理。通过实例展示如何访问和操作这些数据。 **第3章：授权与身份验证** - 授权和身份验证是Web应用安全的核心。本章介绍了flask-login扩展的使用，涉及创建LoginManager、定义用户模型、登录、登出过程，以及未登录用户访问时的处理和会话超时设置。 **第4章：Blueprints（蓝图）** - 蓝图是Flask中模块化的设计，有助于组织大型应用。这里会提供基本蓝图示例，展示如何分解和复用代码。 **第5章：类基础视图（Class-Based Views）** - 类基础视图提供了一种更高级的方式来组织和重用视图函数，本章通过实例展示了其基本用法。 **第6章：自定义Jinja2模板过滤器** - Jinja2是Flask的默认模板引擎，本节介绍了如何创建和使用自定义过滤器，如格式化日期，提升模板的灵活性。 **第7章：部署Flask应用：uWSGI** - 最后，文章探讨了如何利用uWSGI这样的工具部署Flask应用到生产环境，确保高效且可扩展的Web服务运行。这是一篇详尽的Flask入门指南，涵盖了从基础设置到高级特性的全面学习，帮助读者掌握如何构建功能丰富的Python Web应用。无论你是初学者还是经验丰富的开发者，都能在这里找到适合自己的内容。

Chapter 2: Accessing request data

Introduction

When working with an web application it's sometimes important to access data included in the

request, beyond the URL.

In Flask this is stored under the global request object, which you can access in your code via from

flask import request.

Examples

Accessing query string

The query string is the part of a request following the URL, preceded by a ? mark.

Example: https://encrypted.google.com/search?hl=en&q=stack%20overflow

For this example, we are making a simple echo webserver that echos back everything submitted

to it via the echo field in GET requests.

Example: localhost:5000/echo?echo=echo+this+back+to+me

Flask Example:

from flask import Flask, request

app = Flask(import_name=__name__)

@app.route("/echo")

def echo():

to_echo = request.args.get("echo", "")

response = "{}".format(to_echo)

return response

if __name__ == "__main__":

app.run()

Combined form and query string

Flask also allows access to a CombinedMultiDict that gives access to both the request.form and

request.args attributes under one variable.

This example pulls data from a form field name submitted along with the echo field in the query

string.

Flask Example:

https://riptutorial.com/ 5

A users will normally be loaded from a database. The callback must return an object which

represents a user corresponding to the provided ID. It should return None if the ID is not valid.

@login_manager.user_loader

def load_user(user_id):

return User.get(user_id) # Fetch the user from the database

This can be done directly below creating your LoginManager.

A class representing your user

As mentioned the user_loader callback has to return an object which represent a user. What does

that mean exactly? That object can for example be a wrapper around user objects stored in your

database or simply directly a model from your database. That object has to implement the

following methods and properties. That means that if the callback returns your database model

you need to ensure that the mentioned properties and methods are added to your model.

is_authenticated

This property should return True if the user is authenticated, i.e. they have provided valid

credentials. You will want to ensure that the objects which represent your users returned by

the user_loader callback return True for that method.

•

is_active

This property should return True if this is an active user - in addition to being authenticated,

they also have activated their account, not been suspended, or any condition your

application has for rejecting an account. Inactive accounts may not log in. If you don't have

such a mechanism present return True from this method.

•

is_anonymous

This property should return True if this is an anonymous user. That means that your user

object returned by the user_loader callback should return True.

•

get_id()

This method must return a unicode that uniquely identifies this user, and can be used to load

the user from the user_loader callback. Note that this must be a unicode - if the ID is natively

an int or some other type, you will need to convert it to unicode. If the user_loader callback

returns objects from the database this method will most likely return the database ID of this

particular user. The same ID should of course cause the user_loader callback to return the

same user later on.

•

If you want to make things easier for yourself (**it is in fact recommended) you can inherit from

UserMixin in the object returned by the user_loader callback (presumably a database model). You

can see how those methods and properties are implemented by default in this mixin here.

https://riptutorial.com/ 8

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