Eroman: Created page with "= Lecture 4 = introduction to website development with flask. NOTE: you do not need to know this material for the test or to know python in general. It is only for showing h..."

2017-04-27T18:26:39Z

Created page with "= Lecture 4 = introduction to website development with flask. NOTE: you do not need to know this material for the test or to know python in general. It is only for showing h..."

New page

= Lecture 4 =

introduction to website development with flask.

NOTE: you do not need to know this material for the test or to know python in general. It is only for showing how to make a website easily.

== Task 0 ==

copy and paste the example from flask's homepage http://flask.pocoo.org/

then run it, and go the the url printed in your terminal

== Query strings and form data ==

The form data and query string data are acessible from a special <code>request</code> object. This <code>request</code> object is imported, and only has data when it is used inside of a view function.

the data for query strings and forms is in a dictionary like object.

== Task 1 ==

Show the bitcoin price in Euro on a webpage

<source lang="python">import requests
from flask import Flask

def get_btc_price():
r = requests.get('https://api.coindesk.com/v1/bpi/currentprice.json')
data = r.json()
price = data['bpi']['EUR']['rate']
return price

app = Flask(__name__)
app.config['DEBUG'] = True

@app.route("/")
def hello():
return '{} €'.format(get_btc_price())

if __name__ == "__main__":
app.run()
</source>
== HTML Templates ==

To use an HTML template with the default flask configuration, make a directory 'templates' in the same directory as your flask script. you can then put html template in here.

for a script <code>./app.py</code> to use a template <code>./templates/index.html</code>, import <code>render_template</code> from flask: <code>from flask import Flask, render_template</code>

and use the line in your view function <code>return render_template('index.html')</code>

variables in jinja2 templates look like <code>{{ variable_name }}</code>, and can be substituted in the <code>render_template</code> function

<code>return render_template('index.html', variable_name='value')</code>

Flask uses the Jinja2 templating engine. see their documentation for more information

== Task 2 ==

Make a form that asks for name and age, and displays:

'Hi $NAME, you are $AGE years old'

using a post request

<code>app.py</code>

<source lang="python">from flask import Flask, render_template, request

app = Flask(__name__)
app.config['DEBUG'] = True

@app.route("/", methods=['POST', 'GET'])
def hello():
name = request.form.get('name', '')
age = request.form.get('age', '')
if name and age:
return render_template('index.html', name=name, age=age)
else:
return render_template('index.html', name=name, age=age), 400

if __name__ == "__main__":
app.run(port=5000)
</source>
<code>templates/index.html</code>

<pre class="html"><html>
<head>
</head>
<body>
<h1>HTML!</h1>
<p>Hi {{ name }}, you are {{ age }} years old</p>
<form action="/" method="POST">
<label>Age
<input type="text" name="age" />
</label>
<label>Name<input type="text" name="name" /></label>
<button type="submit">submit</button>
</form>
</body>
</html></pre>
== Task 3 ==

make a post request to your application with <code>requests</code> that submits the name and age

<pre>r = requests.post('http://localhost:5000/', data={'name': 'Talvi', 'age': 50})
print(r.text)</pre>

I719 Fundamentals of Python/lecture4v2 - Revision history

Eroman: Created page with "= Lecture 4 = introduction to website development with flask. NOTE: you do not need to know this material for the test or to know python in general. It is only for showing h..."