JSON python get value

Question

How can I get the price value with the get() function instead of using []?

As you can see availableToBack and availableToLay dictionaries can be empty at one point and I am trying to prevent an error when it happens and return None.

u'ex':
    {u'availableToBack':
        [
            {u'price': 1.02,
            u'size': 2.15}
        ],
    u'availableToLay': [],
    u'tradedVolume': []
    }

The way I get price is:

price = ['ex']['availableToBack'][0][price]

But in case of availableToLay it would give a key error. I know there is another way which would give None if value does not exist.

price = get('ex')...

Just can't figure out how construct this complex version of it. Can you hep?

maybe im missing something, but if you replace price = ['ex']['availableToBack'][0][price] with price=ex.get('availableToBack').get(0).get(price) this should do what you want — nathan.medz
– nathan.medz, Commented Feb 25, 2016 at 16:52

Dušan Maďar · Accepted Answer · 2016-02-25 17:19:15Z

1

This approach will get you all available prices.

ex = {'ex':
        {u'availableToBack':
            [
                {u'price': 1.02,
                 u'size': 2.15}
            ],
        u'availableToLay': [],
        u'tradedVolume': []
        }
    }

for ex_list in ex.get('ex', {}).values():
    if not ex_list:
        continue

    for item in ex_list:
        price = item.get('price')

edited Feb 25, 2016 at 17:19

answered Feb 25, 2016 at 17:12

Dušan Maďar

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Comments

mvelay · Accepted Answer · 2016-02-25 17:00:32Z

0

First, you could use json module to convert your json into a python dictionary, you cannot call ex dict the way you are doing.

Then, in order not to except KeyError, you should use get() method that returns None (by default) if the key does not exist

edited Feb 25, 2016 at 17:00

answered Feb 25, 2016 at 16:51

mvelay

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1 Comment

idjaw Over a year ago

Not quite. If you fail on your first get, and default to None, every subsequent call will fail. There needs to be a better check, or even better, just wrap with a try/except indicating that the key could not be found.

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