urlencode an array of values

Question

I'm trying to urlencode an dictionary in python with urllib.urlencode. The problem is, I have to encode an array.

The result needs to be:

criterias%5B%5D=member&criterias%5B%5D=issue
#unquoted: criterias[]=member&criterias[]=issue

But the result I get is:

criterias=%5B%27member%27%2C+%27issue%27%5D
#unquoted: criterias=['member',+'issue']

I have tried several things, but I can't seem to get the right result.

import urllib
criterias = ['member', 'issue']
params = {
    'criterias[]': criterias,
}
print urllib.urlencode(params)

If I use cgi.parse_qs to decode a correct query string, I get this as result:

{'criterias[]': ['member', 'issue']}

But if I encode that result, I get a wrong result back. Is there a way to produce the expected result?

cig.parse_qs is deprecated (only retained for backward compatibility), so it may be better to use urlparse.parse_qs — ChristopheD
– ChristopheD, Commented Apr 3, 2010 at 11:59
Thanks for the tip. I only used it for comparison, so it's not really used. — Ikke
– Ikke, Commented Apr 3, 2010 at 12:03

smac89 · Accepted Answer · 2024-09-13 13:23:22Z

91

The solution (for Python 2) is far simpler than the ones listed above.

>>> import urllib
>>> params = {'criterias[]': ['member', 'issue']}
>>> 
>>> print urllib.urlencode(params, True)
criterias%5B%5D=member&criterias%5B%5D=issue

Note the True. See http://docs.python.org/library/urllib.html#urllib.urlencode the doseq variable.

As a side note, you do not need the [] for it to work as an array (which is why urllib does not include it). This means that you do not not need to add the [] to all your array keys.

edited Sep 13, 2024 at 13:23

smac89

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answered Apr 19, 2012 at 17:05

CSTobey

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5 Comments

Martin Gerhardy Over a year ago

If you don't add the [], php will only use criterias=issue, and will ignore the "member"

Martin Gerhardy Over a year ago

Also see the answer for this question: stackoverflow.com/questions/6243051/…

CSTobey Over a year ago

To clarify, Python doesn't care if the []'s are there: it will convert it correctly regardless. But yes, PHP (and maybe other languages?) does care, so if you have an external dependency on such systems, it is best to leave the []'s... it just looks weird in Python.

Tom Russell Over a year ago

Amazing. I was sure this was going to be difficult!

brotskydotcom Over a year ago

In Python 3 the urllib module has been broken up and the urlencode entry is in the parse submodule. The docs are now at: docs.python.org/3/library/…

Lukáš Lalinský · Accepted Answer · 2010-04-03 12:00:25Z

12

You can use a list of key-value pairs (tuples):

>>> urllib.urlencode([('criterias[]', 'member'), ('criterias[]', 'issue')])
'criterias%5B%5D=member&criterias%5B%5D=issue'

answered Apr 3, 2010 at 12:00

Lukáš Lalinský

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3 Comments

Lukáš Lalinský Over a year ago

Well, it's very easy to write a function that transforms the dict with lists into a list of tuples.

dlrust Over a year ago

just a note for others, to generate the urlencoded string straight from a regular dict, all you need to do is urllib.urlencode(d.items())

Lukáš Lalinský Over a year ago

You don't even need to do that, urllib.urlencode(d) should work fine.

David · Accepted Answer · 2010-10-25 23:57:52Z

To abstract this out to work for any parameter dictionary and convert it into a list of tuples:

import urllib

def url_encode_params(params={}):
    if not isinstance(params, dict): 
        raise Exception("You must pass in a dictionary!")
    params_list = []
    for k,v in params.items():
        if isinstance(v, list): params_list.extend([(k, x) for x in v])
        else: params_list.append((k, v))
    return urllib.urlencode(params_list)

Which should now work for both the above example as well as a dictionary with some strings and some arrays as values:

criterias = ['member', 'issue']
params = {
    'criterias[]': criterias,
}
url_encode_params(params)
>>'criterias%5B%5D=member&criterias%5B%5D=issue'

gimel · Accepted Answer · 2010-04-03 12:04:27Z

2

Listcomp of values:

>>> criterias = ['member', 'issue']
>>> urllib.urlencode([('criterias[]', i) for i in criterias])
'criterias%5B%5D=member&criterias%5B%5D=issue'
>>>

answered Apr 3, 2010 at 12:04

gimel

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Comments

ZhiQiang Fan · Accepted Answer · 2019-06-11 03:22:00Z

1

as aws api defines its get url: params.0=foo&params.1=bar

however, the disadvantage is that you need to write code to encode and decode by your own, the result is: params=[foo, bar]

answered Jun 11, 2019 at 3:22

ZhiQiang Fan

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Comments

smac89 · Accepted Answer · 2024-09-13 13:30:01Z

0

With Python3, the best way to do this is the following:

from urllib.parse import urlencode

criterias = ['member', 'issue']
print (urlencode(dict(criterias=criterias), doseq=True))

Another method that works is:

print (urlencode([('criterias', criterias)], doseq=True))

Both will produce the following result:

criterias=member&criterias=issue

answered Sep 13, 2024 at 13:30

smac89

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