上下文处理器（context_processor钩子函数）

1、app.py

from flask import Flask, render_template, g

app = Flask(__name__)

@app.route('/')
def index():
    return render_template('index.html')

@app.route('/article/')
def article():
    return render_template('article.html')

@app.context_processor
def context_processor():
    g.username = 'admin'
    return {'username': g.username}

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

2、index.html

{{ username }}

3、article.html

{{ username }}