14.8. Web Applications With a User Interface¶
This section builds on the material in the preceding sections to present a web application that prompts the user to provide input, performs some processing, and displays results.
1 from flask import Flask, request
2
3 app = Flask(__name__)
4
5 @app.route('/')
6 def home():
7 return HOME_HTML
8
9 HOME_HTML = """
10 <html><body>
11 <h2>Welcome to the Greeter</h2>
12 <form action="/greet">
13 What's your name? <input type='text' name='username'><br>
14 What's your favorite food? <input type='text' name='favfood'><br>
15 <input type='submit' value='Continue'>
16 </form>
17 </body></html>"""
18
19 @app.route('/greet')
20 def greet():
21 username = request.args.get('username', '')
22 favfood = request.args.get('favfood', '')
23 if username == '':
24 username = 'World'
25 if favfood == '':
26 msg = 'You did not tell me your favorite food.'
27 else:
28 msg = 'I like ' + favfood + ', too.'
29
30 return GREET_HTML.format(username, msg)
31
32 GREET_HTML = """
33 <html><body>
34 <h2>Hello, {0}!</h2>
35 {1}
36 </body></html>
37 """
38
39 if __name__ == "__main__":
40 # Launch the Flask dev server
41 app.run(host="localhost", debug=True)
The program is organized as follows:
Lines 6-8 define the
home()function, which defines the starting page for the application. It displays a form that prompts for the user’s name and favorite food.The form’s
actionattribute on Line 13 specifies that the form submission will be directed to the path /greet. Processing for this path is defined by thegreet()function on lines 20-31.Lines 22-29 extract the information submitted on the form and compute a response message.
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