Python Requests: Using lists when specifying parameters

Question

Trying to fetch currency quotes from Oanda's API. Here is the code I have:

s = requests.Session()
url = "https://stream-fxpractice.oanda.com/v1/prices"
headers = {'Authorization': 'Bearer ' + access_token}
params = {'instruments': pairs_oanda, 'accountId': account_id}
resp = s.get(url, headers=headers, params=params, stream=True)

The access_token and account_id are authentication for the API. When I supply one currency pair, for instance "EUR_USD", to pairs_oanda it works fine, resulting in the following url:

https://streamfxpractice.oanda.com/v1/prices?instruments=GBP_USD&accountId=*******

However, when I supply a list of currency pairs, for instance

["EUR_USD", "GBP_USD"]

to pairs_oanda, I get this URL:

https://stream-fxpractice.oanda.com/v1/prices?instruments=EUR_USD&instruments=GBP_USD&accountId=*******

However, what I need the url to look like to properly access the API is this:

https://stream-fxpractice.oanda.com/v1/prices?instruments=EUR_USD%2CGBP_USD&accountId=*******

Is there anyway to get Requests to parse the list differently?

Martijn Pieters · Accepted Answer · 2015-07-02 20:18:20Z

4

The API wants you to use a comma to separate the currency pairs. You'll have to do so yourself; use str.join() here:

pairs_oanda = ["EUR_USD", "GBP_USD"]
params = {'instruments': ','.join(pairs_oanda), 'accountId': account_id}

The %2C character sequence is a , encoded to URL encoding:

>>> from urlparse import unquote
>>> unquote('%2C')
','

and requests takes care of quoting for you provided you give it the unquoted parameter values:

>>> from requests import Request
>>> url = "https://stream-fxpractice.oanda.com/v1/prices"
>>> pairs_oanda = ["EUR_USD", "GBP_USD"]
>>> params = {'instruments': ','.join(pairs_oanda), 'accountId': 'foobarbaz'}
>>> r = Request('GET', url, params=params)
>>> r.prepare().url
'https://stream-fxpractice.oanda.com/v1/prices?instruments=EUR_USD%2CGBP_USD&accountId=foobarbaz'

answered Jul 2, 2015 at 20:18

Martijn Pieters

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1 Comment

eadains Over a year ago

Ah, there we go. Bit new to the website, as you can probably tell. Thanks for the help

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