CODEWITHSUNDEEP
python-3.x
kh99
kh99

Reputation: 41

How to get max value key from a list with each element of list is a dictionary?

I'm trying to get maximum value key from a list with each element of list is a dictionary like

li = [{'a': 100}, {'b': 200}, {'c': 50}]

Is it possible to get maximum value key without sorting list? Please help me to solve this.

Upvotes: 1

Views: 113

Answers (3)

tonedblue
tonedblue

Reputation: 164

You can get the maximum value in linear time by accessing each element and saving the current maximum value. Edit

People already wrote the pythonic way of doing it. The non pythonic way would be to write a normal loop like this:

li = [{'a': 100}, {'b': 200}, {'c': 50}]

# if you know that all numbers are positive then just use max = 0
max = list(li[0].values())[0]

for values in li:    
    for value in values.values():
        if value > max:
           max = value

Upvotes: 1

hiro protagonist
hiro protagonist

Reputation: 46849

this would also allow for more items in your dictionaries:

from itertools import chain
from operator import itemgetter
li = [{'a': 100}, {'b': 200}, {'c': 50}]
m = max(chain.from_iterable(item.items() for item in li), key=itemgetter(1))[0]
print(m)

i.e. it would also work if your list looked like this:

li = [{'a': 100}, {'b': 200, 'd': 50}, {'c': 50, 'e': 300, 'f': 20}]

you'd need to take edge-cases like

li = [{'a': 100}, {'b': 100}]

into account. should the answer be a or b?

Upvotes: 1

kabanus
kabanus

Reputation: 25895

The max built-in accepts a key parameter which can be as complex as you want it:

max(li,key=lambda x: list(x.values())[0])

If all your dictionaries have one item, then just get all the values, and retrieve the first (and only) index. Note in Python 2 values() returns a view, so you have to convert it to a list before accessing it.

Upvotes: 1

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