Python 和 Flask Web 应用程序（入门教程）

原文： https://pythonspot.com/flask-web-app-with-python/

51.md - 图1

使用 Flask 创建的 Python 应用

在本教程中，您将学习如何使用 Python 构建网络应用。我们将使用称为 Flask 的微型框架。

为什么是 Flask？

易于使用。
内置开发服务器和调试器
集成单元测试支持
RESTful 请求分派
使用 Jinja2 模板
支持安全 cookie（客户端会话）
100％符合 WSGI 1.0
基于 Unicode
大量记录

创建 URL 路由

URL 路由使 Web 应用程序中的 URL 易于记住。现在，我们将创建一些 URL 路由：

/hello
/members/
/members/name/

复制下面的代码，并将其另存为app.py

from flask import Flask
app = Flask(__name__)
@app.route("/")
def index():
    return "Index!"
@app.route("/hello")
def hello():
    return "Hello World!"
@app.route("/members")
def members():
    return "Members"
@app.route("/members/<string:name>/")
def getMember(name):
    return name</string:name>
if __name__ == "__main__":
    app.run()

使用以下命令重新启动应用程序：

$ python hello.py
* Running on http://localhost:5000/

在浏览器中尝试网址：

51.md - 图2

python-flask-webapp

Flask 页面模板

我们将使用称为模板的技术将代码和用户界面分开。我们创建名为/templates/的目录并创建模板：


<h1>Hello {{name}}</h1>

Python Flask 应用具有新的 URL 路由。我们将默认端口更改为 80，即默认 HTTP 端口：

from flask import Flask, flash, redirect, render_template, request, session, abort
app = Flask(__name__)
@app.route("/")
def index():
    return "Flask App!"
@app.route("/hello/<string:name>/")
def hello(name):
    return render_template(
    'test.html',name=name)</string:name>
if __name__ == "__main__":
    app.run(host='0.0.0.0', port=80)

You can then open : http://127.0.0.1/hello/Jackson/

给模板添加样式

您是否需要一些外观更好的模板？我们修改文件：

{% extends "layout.html" %};
{% block body %};
<div class="block1">
<h1>Hello {{name}}!</h1>
<h2>Here is an interesting quote for you:</h2>
"The limits of my language are the limits of my mind. All I know is what I have words for."
<img src="http://www.naturalprogramming.cimg/smilingpython.gif">
</div>
{% endblock %};

然后，我们创建layout.html来定义页面的外观。（您可能想要拆分样式表和layout.html文件）。将此复制为layout.html


<title>Website</title>
<style>
@import url(http://fonts.googleapis.com/css?family=Amatic+SC:700);</p>
<p>body{<br />
    text-align: center;<br />
}<br />
h1{<br />
    font-family: 'Amatic SC', cursive;<br />
    font-weight: normal;<br />
    color: #8ac640;<br />
    font-size: 2.5em;<br />
}</p>
</style>{% block body %};{% endblock %};

重新启动应用程序并打开 URL：http://127.0.0.1/hello/Jackson/，您可以选择杰克逊以外的任何其他名字。

51.md - 图3

python webapp flask

传递变量

让我们显示随机引文，而不是总是相同的引文。我们将需要同时传递name变量和quote变量。要将多个变量传递给函数，我们只需执行以下操作：

    return render_template(
'test.html',**locals())

我们新的test.html模板如下所示：

{% extends "layout.html" %};
{% block body %};
<div class="block1">
<h1>Hello {{name}}!</h1>
<h2>Here is an interesting quote for you:</h2>
{{quote}}
<img src="http://www.naturalprogramming.cimg/smilingpython.gif">
</div>
{% endblock %};

我们将需要选择一个随机引文。为此，我们使用以下代码：

    quotes = [ "'If people do not believe that mathematics is simple, it is only because they do not realize how complicated life is.' -- John Louis von Neumann ",
"'Computer science is no more about computers than astronomy is about telescopes' --  Edsger Dijkstra ",
"'To understand recursion you must first understand recursion..' -- Unknown",
"'You look at things that are and ask, why? I dream of things that never were and ask, why not?' -- Unknown",
"'Mathematics is the key and door to the sciences.' -- Galileo Galilei",
"'Not everyone will understand your journey. Thats fine. Its not their journey to make sense of. Its yours.' -- Unknown"  ]
randomNumber = randint(0,len(quotes)-1)
quote = quotes[randomNumber]

您看到的第一件事是我们定义了一个包含多个引文的数组。这些可以作为quote[0]，quote[1]，quote[2]等访问。函数randint()返回一个介于 0 和引文总数之间的随机数，因为我们从零开始计数，所以减去了一个。最后，我们将quote变量设置为计算机选择的引文。将以下代码复制到app.py：

from flask import Flask, flash, redirect, render_template, request, session, abort
from random import randint
app = Flask(__name__)
@app.route("/")
def index():
    return "Flask App!"
#@app.route("/hello/<string:name>")
@app.route("/hello/<string:name>/")
def hello(name):
    #    return name
quotes = [ "'If people do not believe that mathematics is simple, it is only because they do not realize how complicated life is.' -- John Louis von Neumann ",
"'Computer science is no more about computers than astronomy is about telescopes' --  Edsger Dijkstra ",
"'To understand recursion you must first understand recursion..' -- Unknown",
"'You look at things that are and ask, why? I dream of things that never were and ask, why not?' -- Unknown",
"'Mathematics is the key and door to the sciences.' -- Galileo Galilei",
"'Not everyone will understand your journey. Thats fine. Its not their journey to make sense of. Its yours.' -- Unknown"  ]
randomNumber = randint(0,len(quotes)-1)
quote = quotes[randomNumber] </string:name></string:name>
return render_template(
    'test.html',**locals())
if __name__ == "__main__":
    app.run(host='0.0.0.0', port=80)

重新启动应用程序时，它将随机返回这些引文之一。

51.md - 图4

python flask webap

下载应用程序以及更多 Flask 示例

接下来是什么？

您可以将您的站点链接到数据库系统，例如 MySQL，MariaDb 或 SQLite。您可以在中找到 SQLite 教程。享受创建您的应用程序的乐趣！

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