How to loop through this Python dict and search if value is there

Question

I have a Python dict like this:

{
    'TagList': [
        {
            'Key': 'tag1',
            'Value': 'val'
        },
        {
            'Key': 'tag2',
            'Value': 'val'
        },
        {
            'Key': 'tag3',
            'Value': 'val'
        },
        ...
    ]
}

How do I loop through this dict to search if the Key tag1 is available.

EDIT: @Willem Van Onsem's solution works great. But I forgot to mention that I need to check more than 1 Key, so for example:

If Tag1 and Tag2 exist => true
If either Tag1 or Tag2 is missing` => false

do you have more keys than 'TagList' in your dict?

lmiguelvargasf
– lmiguelvargasf

2017-07-14 17:45:48 +00:00
Commented Jul 14, 2017 at 17:45 — lmiguelvargasf
– lmiguelvargasf, Commented Jul 14, 2017 at 17:45
No only 1 key like TagList

Casper
– Casper

2017-07-14 17:47:07 +00:00
Commented Jul 14, 2017 at 17:47 — Casper
– Casper, Commented Jul 14, 2017 at 17:47

willeM_ Van Onsem · Accepted Answer · 2017-07-14 17:58:14Z

5

Assuming that your dictionary contains a key 'TagList' and you are only interested in the dictionaries in the list associated with that key, you can use:

any(subd.get('Key') == 'tag1' for subd in the_dict['TagList'])

Where the dictionary the_dict is the one you want to inspect.

We thus use the any(..) builtin with a generator expression that iterates through the list associated with the 'TagList' key. For each such subdictionary, we check if the key 'Key' is associated with the value 'tag1'. In case no key 'Key' is present in one or more of the subdictionaries, that is not a problem since we use .get(..).

For your given dictionary, this generates:

>>> any(subd.get('Key') == 'tag1' for subd in the_dict['TagList'])
True

Multiple values

If you want to check that all values of a list occur in the subdictionaries, we can use the following two-liner (given the "tag names" are hashable, strings are hashable):

tag_names = {subd.get('Key') for subd in the_dict['TagList']}
all(tag in tag_names for tag in ('tag1','tag2'))

Here the all(..) will return True if all the tag names in the tuple at the right (('tag1','tag2')) are each in at least one subdictionary.

For example:

>>> all(tag in tag_names for tag in ('tag1','tag2'))
True
>>> all(tag in tag_names for tag in ('tag1','tag2','tag3'))
True
>>> all(tag in tag_names for tag in ('tag1','tag2','tag4'))
False

edited Jul 14, 2017 at 17:58

answered Jul 14, 2017 at 17:46

willeM_ Van Onsem

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5 Comments

Casper Over a year ago

Thanks, this 1-line solution works great. Can I add another condition to this code to check if both tag1 "and" tag2 are there?

willeM_ Van Onsem Over a year ago

@Casper: that's a harder problem. But it is possible. I will edit the answer.

Casper Over a year ago

Wow many thanks, I never knew about these elegant functions of Python, now I can get rid of those for loops...

Casper Over a year ago

@WillemVanOnsem hi Willem, I stumbled upon this new format and the current answer doesn't seem to apply. { 'Tags': { 'Key': 'Value' } } I want to check if the value 'Key' matches my search key

willeM_ Van Onsem Over a year ago

@Casper: please edit your question, or ask a new one.

lmiguelvargasf · Accepted Answer · 2017-07-14 17:48:49Z

2

You can use the following loop:

for key in d:
    for item in d[key]:
        for deep_key in item:
            if item[deep_key] == 'tag1': # whatever you are looking for
                print('Found')

answered Jul 14, 2017 at 17:48

lmiguelvargasf

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Comments

frogcoder · Accepted Answer · 2017-07-14 17:51:12Z

0

from collections import ChainMap

'tag1' in ChainMap(*d['TagList'])

or if you want the tag1's value

ChainMap(*d['TagList'])['tag1']

answered Jul 14, 2017 at 17:51

frogcoder

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Comments

R.A.Munna · Accepted Answer · 2017-07-14 20:42:13Z

0

If you declare your dictionary as a_dict then their is the other way to find the Key tag1. If found then it will return the True else False.

tag_list = a_dict['TagList']
result = next((True for item in tag_list if item["Key"] == "tag1"),False)
print(result)

for multiple :

a,b=next((True for item in tag_list if item["Key"] == "ta1"),False),\
    next((True for item in tag_list if item["Key"] == "tag2"), False)
result = a and b
print(result)

edited Jul 14, 2017 at 20:42

answered Jul 14, 2017 at 18:21

R.A.Munna

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