Install Python Flask: Get your web app started successfully

Python Flask is a lightweight web application framework that uses Python as the main development language. It is simple and flexible, suitable for quickly building web applications. In this article, we will introduce how to install and configure Python Flask, and provide some specific code examples to help you quickly launch your web application.

1. Install Python Flask
To install Python Flask, you first need to make sure that Python is installed on your machine. You can check whether Python is installed by entering the following command in the terminal:

python --version

If Python is already installed, you will see the version number of Python. If it is not installed, you can download and install the latest version from Python's official website.

After installing Python, we can use pip (Python's package management tool) to install Flask. Just enter the following command in the terminal:

pip install flask

After the installation is complete, you can start using Python Flask to build web applications.

2. Simple example
To help you get started with Python Flask quickly, we provide a simple example code. First, create a file named app.py in your project folder and enter the following code in it:

from flask import Flask

# 创建Flask应用对象
app = Flask(__name__)

# 定义路由
@app.route('/')
def hello_world():
    return 'Hello, World!'

# 启动应用
if __name__ == '__main__':
    app.run()

In the above code, we first imported the Flask module and created a Flask application object . Then, we define a route that when accessing the root path '/', the hello_world() function will be executed and a simple string will be returned. Finally, we call the app.run() method to start the application.

Save and run the app.py file, you will see some information output from the terminal, telling you that the Flask application is already running. You can visit http://localhost:5000/ in the browser and you will see the sentence "Hello, World!" displayed on the web page.

3. More complex examples
Python Flask can not only return simple strings, but also create more complex web applications. Here is a more complex example code that shows how to create a simple blogging application in Flask:

from flask import Flask, render_template, request

app = Flask(__name__)

# 定义主页路由
@app.route('/')
def index():
    return render_template('index.html')

# 定义博客详情页路由
@app.route('/blog/<int:blog_id>')
def blog_detail(blog_id):
    # 通过 blog_id 查询数据库获取博客详情
    # ...
    return render_template('blog_detail.html', blog=blog)

# 定义搜索路由
@app.route('/search', methods=['POST'])
def search():
    keyword = request.form.get('keyword')
    # 通过关键字搜索数据库获取相关博客
    # ...
    return render_template('search_result.html', blogs=blogs)

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

In the above code, we have created three different routes. The homepage route ('/') returns an HTML template, and the blog details page route ('/blog/') receives a parameter blog_id, and queries the blog details from the database based on this parameter and returns the corresponding HTML template. . The search route ('/search') uses the POST method to receive the keywords entered by the user, then searches for relevant blogs from the database based on the keywords and returns the HTML template of the search results.

You need to use a template language to write HTML templates. Here we use the Jinja2 template engine built into Flask. You can learn more about how to use Jinja2 in the official documentation. In addition, you also need to install Flask's dependency packages Flask-Jinja2 and Flask-WTF through pip.

Run the sample code and you can see different pages by accessing different routes. You can extend and improve this blogging application according to your needs.

Summary
This article introduces how to install Python Flask and provides some simple and complex sample code. Python Flask is a very simple and flexible web application framework, suitable for quickly building various types of web applications. I hope this article can help you quickly get started with Python Flask and start your own web application.

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