3.4 控制语句
常用的几种控制语句：
模板中的if控制语句
@app.route('/user') def user(): user = 'dongGe' return render_template('user.html',user=user) <html> <head> {% if user %} <title> hello {{user}} </title> {% else %} <title> welcome to flask </title> {% endif %} </head> <body> <h1>hello world</h1> </body> </html>
模板中的for循环语句
@app.route('/loop') def loop(): fruit = ['apple','orange','pear','grape'] return render_template('loop.html',fruit=fruit) <html> <head> {% if user %} <title> hello {{user}} </title> {% else %} <title> welcome to flask </title> {% endif %} </head> <body> <h1>hello world</h1> <ul> {% for index in fruit %} <li>{{ index }}</li> {% endfor %} </ul> </body> </html>