How to access dictionary-type items in a list (python or maybe javascript)

Question

I have some data stored in 'nutrients' JSONField in a django 'Food' model.

some sample datastructure at the bottom.

The data is Food.nutrients, but I don't know how/ best way access a particular item in the nutrients list - which is structured like [{dict type item},{dict type item},...].

Each item is a dictionary with a 'name' key and 'nutrient_id' key, which I feel could help me pick out the item that I want. And then from the item dictionary I want to get the value for key 'value' (I didn't name the key 'value').

 [{u'dp': 1,
  u'group': u'Minerals',
  u'measures': [],
  u'name': u'Manganese, Mn',
  u'nutrient_id': 315,
  u'se': u'',
  u'sourcecode': [1],
  u'unit': u'mg',
  u'value': 0.094},
 {u'dp': 1,
  u'group': u'Minerals',
  u'measures': [],
  u'name': u'Selenium, Se',
  u'nutrient_id': 317,
  u'se': u'',
  u'sourcecode': [1],
  u'unit': u'\xb5g',
  u'value': 0.4},
 {u'dp': 1,
  u'group': u'Vitamins',
  u'measures': [],
  u'name': u'Vitamin C, total ascorbic acid',
  u'nutrient_id': 401,
  u'se': u'',
  u'sourcecode': [1],
  u'unit': u'mg',
  u'value': 4.0}]

masnun · Accepted Answer · 2016-08-13 11:05:54Z

4

Let's suppose, you have the list of dictionaries in nutrients. Now you can filter the list to find the items matching a particular key with a specific value. For example, to find the dictionary with name having "Manganese, Mn", you can do:

matches = filter(lambda n: n.get('name') == 'Manganese, Mn', nutrients)

Now the matches list should contain the nutrients which contain "Manganese, Mn" in the name key.

You can access the first nutrient using index - matches[0]. Now you can access other keys too, like matches[0].get('value')

answered Aug 13, 2016 at 11:05

masnun

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3 Comments

amchugh89 Over a year ago

Awesome - thanks a lot. works, and it's a pretty little oneliner

amchugh89 Over a year ago

I realized this is the equivalent of [n for n in nutrients where n.get('name') == 'Manganese,Mn'] which is incidentally the way I prefer, but I speed tested it and this [n for n..] "pythonic" way is actually a bit faster in this case as well

masnun Over a year ago

Yes, they are equivalent.

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