How can I get value of the nested dictionary using ImmutableMultiDict on Flask?

Question

address_dict = {'address': {'US': 'San Francisco', 'US': 'New York', 'UK': 'London'}}

When above parameters was sent via requests, how can I get values in address key using request.form on Flask?

import requests
url =  'http://example.com'
params = {"address": {"US": "San Francisco", "UK": "London", "CH": "Shanghai"}}
requests.post(url, data=params) 

Then I got this in context of flask.request.

ImmutableMultiDict([('address', u'US'), ('address', 'US'), ('address', 'UK')])

How can I get the value in each key of addresses?

Thanks.

Answer 1

for example like this:

from werkzeug.datastructures import ImmutableMultiDict
imd = ImmutableMultiDict([('address', u'US'), ('address', 'US'), ('address', 'UK')])
print imd.getlist('address')

prints:

[u'US', 'US', 'UK']

---

edit:

Your POST-request is sent application/x-www-form-urlencoded, which means as combination as key/value pairs. It doesn't support a nested dict structure directly. When i try your curl-request I get this:

ImmutableMultiDict([('address[US]', u'San Francisco'), ('address[US]', u'New York'), ('address[UK]', u'London')])

so the keys are interpreted literally here.

and using urllib2 i get this result:

>>> print urllib2.urlopen("http://localhost:5000/post", data=urllib.urlencode(address_dict)).read()
ImmutableMultiDict([('address', u"{'UK': 'London', 'US': 'New York'}")])

here urlencode simply sends a string representation of the inner dict.

and finally using requests:

>>> print requests.post("http://localhost:5000/post", data=address_dict).content
ImmutableMultiDict([('address', u'UK'), ('address', u'US')])

here the array is flattened and recurring keys eliminated.

There is simply no defined way how to send a nested dict like yours in an urlencoded way, so you'll have to find another solution.

Answer 2

You gave this example:

curl http://example.com -d "address[US]=San Francisco" -d "address[US]=New York" -d address[UK]=London"

With such a request, request.form would look like this:

>>> request.form
ImmutableMultiDict([('address[US]', u'San Francisco'), ('address[US]', u'New York'),
                    ('address[UK]', u'London')])
>>> request.form['address[US]']
u'San Francisco'
>>> request.form.getlist('address[US]')
[u'San Francisco', u'New York']

The [ and ] characters are not special, they are just part of the keys. As documented, a MultiDict will map each key not just to one value but to a list of values. Normal dictionnary access with [] will only give you the first key, but the getlist() method gives the whole list for one key. Other methods are available, see the docs.

If you really want a nested structure, try JSON instead of flat form data.