CODEWITHSUNDEEP
pythondictionarydictionary-comprehension
Jesse O
Jesse O

Reputation: 431

Selecting elements of a Python dictionary greater than a certain value

I need to select elements of a dictionary of a certain value or greater. I am aware of how to do this with lists, Return list of items in list greater than some value.

But I am not sure how to translate that into something functional for a dictionary. I managed to get the tags that correspond (I think) to values greater than or equal to a number, but using the following gives only the tags:

[i for i in dict if dict.values() >= x]

Upvotes: 42

Views: 133242

Answers (3)

nmaier
nmaier

Reputation: 33192

.items() will return (key, value) pairs that you can use to reconstruct a filtered dict using a list comprehension that is feed into the dict() constructor, that will accept an iterable of (key, value) tuples aka. our list comprehension:

>>> d = dict(a=1, b=10, c=30, d=2)
>>> d
{'a': 1, 'c': 30, 'b': 10, 'd': 2}
>>> d = dict((k, v) for k, v in d.items() if v >= 10)
>>> d
{'c': 30, 'b': 10}

If you don't care about running your code on python older than version 2.7, see @opatut answer using "dict comprehensions":

{k:v for (k,v) in dict.items() if v > something}

Upvotes: 57

Shashank
Shashank

Reputation: 13869

You want dict[i] not dict.values(). dict.values() will return the whole list of values that are in the dictionary.

dict = {2:5, 6:2}
x = 4
print [dict[i] for i in dict if dict[i] >= x] # prints [5]

Upvotes: 9

opatut
opatut

Reputation: 6864

While nmaier's solution would have been my way to go, notice that since python 2.7+ there has been a "dict comprehension" syntax:

{k:v for (k,v) in dict.items() if v > something}

Found here: Create a dictionary with list comprehension in Python. I found this by googling "python dictionary list comprehension", top post.

Explanation

  • { .... } includes the dict comprehension
  • k:v what elements to add to the dict
  • for (k,v) in dict.items() this iterates over all tuples (key-value-pairs) of the dict
  • if v > something a condition that has to apply on every value that is to be included

Upvotes: 22

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