Find out max value from a python dict

Question

I am new to python and I am having a dict. I would like to find out the maximum valued fields from the dict like for index 0 and 1 there is a common value in the dict i.e 1. So I would like to identify the max value which is 0.8 and to be pointed out.

 0: ['1', 'Metrolink', 0.7054569125175476],
 1: ['1', 'Toronto', 0.8],

Like wise I would like to do the same for all other values.

This is my complete dict.

 d={
 0: ['1', 'Metrolink', 0.7054569125175476],
 1: ['1', 'Toronto', 0.8],
 4: ['2', 'Residence Inn Bentonville', 0.721284806728363],
 5: ['2', 'Bentonville, Arkansas', 0.8],
 7: ['2', 'Rogers', 0.5609406232833862],
 8: ['2', 'Toronto', 0.8],
 10: ['2', 'Arkansas', 0.8871413469314575],
 12: ['2', 'CA', 0.5339972972869873],
 14: ['3', 'Toronto', 0.8],
 19: ['3', 'ik', 0.555569052696228],
 21: ['4', 'DL', 0.47785162925720215],
 22: ['4', 'MS', 0.5182732939720154],
 23: ['4', 'Nashville International Airport', 0.8],
 27: ['4', 'Turkey', 0.8],
 30: ['5', 'Hebron, Kentucky', 0.8],
 32: ['5', 'OAK PARK', 0.6157999038696289],
 35: ['5', 'USA', 0.5055036544799805],
 36: ['5', 'Tennessee', 0.5752009153366089],
 37: ['5', 'Recov', 0.6585434675216675],
 38: ['5', 'County (United States)', 0.8],
 40: ['6', 'SFO', 0.6019220948219299],
 42: ['6', 'Ontario', 0.8],
 45: ['7', 'United States', 0.6973987221717834],
 47: ['7', 'Buckingham Gate', 0.8],
 48: ['7', 'London', 0.9545853137969971],
 53: ['8', 'Phoenix, Arizona', 0.8],
 55: ['8', 'STE', 0.5046005249023438],
 56: ['8', 'TULSA', 0.7144339680671692],
 58: ['8', 'UNITED STATES OF AMERICA', 0.8454625606536865],
 60: ['9', 'RDU', 0.6373313069343567],
 61: ['9', 'Raleigh–Durham International Airport', 0.8],
 65: ['9', 'Piauí', 0.8],
 69: ['9', 'CAR', 0.6243148446083069],
 71: ['10', 'MONMOUTH JUNCTION', 0.7259661555290222],
 72: ['10', 'New Jersey', 0.8],
 76: ['10', 'PVK', 0.6593300104141235],
 79: ['10', 'TWW', 0.6495188474655151],
 81: ['10', 'Morrisville, Bucks County, Pennsylvania', 0.8],
 84: ['10', 'United States', 0.8],
 88: ['10', 'New Brunswick, New Jersey', 0.8]

Does this answer your question? [Getting key with maximum value in dictionary?](https://stackoverflow.com/questions/268272/getting-key-with-maximum-value-in-dictionary) — mpx, Jul 20 '20 at 05:35

score 2 · Accepted Answer · answered Jul 20 '20 at 06:11

Pandas is very effective tool for handling tabular data like this. You could create a pandas DataFrame from the data:

import pandas as pd
df = pd.DataFrame(d).T
df.columns = ('group', 'place', 'value')

and then just print out the maximum values

df[df['value'] == df.groupby('group')['value'].transform('max')]

which gives

Out[41]:
   group                                    place     value
1      1                                  Toronto       0.8
10     2                                 Arkansas  0.887141
14     3                                  Toronto       0.8
23     4          Nashville International Airport       0.8
27     4                                   Turkey       0.8
30     5                         Hebron, Kentucky       0.8
38     5                   County (United States)       0.8
42     6                                  Ontario       0.8
48     7                                   London  0.954585
58     8                 UNITED STATES OF AMERICA  0.845463
61     9      RaleighDurham International Airport       0.8
65     9                                    Piauí       0.8
72    10                               New Jersey       0.8
81    10  Morrisville, Bucks County, Pennsylvania       0.8
84    10                            United States       0.8
88    10                New Brunswick, New Jersey       0.8

If you want to get the output in the original format, you can use df.to_dict

In [47]: df[df['value'] == df.groupby('group')['value'].transform('max')].T.to_dict(orient='list')
Out[47]:
{1: ['1', 'Toronto', 0.8],
 10: ['2', 'Arkansas', 0.8871413469314575],
 14: ['3', 'Toronto', 0.8],
 23: ['4', 'Nashville International Airport', 0.8],
 27: ['4', 'Turkey', 0.8],
 30: ['5', 'Hebron, Kentucky', 0.8],
 38: ['5', 'County (United States)', 0.8],
 42: ['6', 'Ontario', 0.8],
 48: ['7', 'London', 0.9545853137969971],
 58: ['8', 'UNITED STATES OF AMERICA', 0.8454625606536865],
 61: ['9', 'RaleighDurham International Airport', 0.8],
 65: ['9', 'Piauí', 0.8],
 72: ['10', 'New Jersey', 0.8],
 81: ['10', 'Morrisville, Bucks County, Pennsylvania', 0.8],
 84: ['10', 'United States', 0.8],
 88: ['10', 'New Brunswick, New Jersey', 0.8]}

Short explanation

Pandas dataframes can be created using dictionaries as arguments. The values should be lists. The .T takes just transpose of the table.
The df.groupby('group')['value'] returns a SeriesGroupBy object, which behaves very much like a regular pandas.Series object. With that we can calculate the maximum value for each group, using the transform method.
The df['value'] == df.groupby('group')['value'].transform('max') creates a boolean mask for selecting the maximum rows by df[mask].

Good solution, can also use `transform(max)` instead of `transform('max')` — Mario Ishac, Jul 20 '20 at 06:23

Mario Ishac · Answer 2 · 2020-07-20T05:47:32.343

0

It sounds like you want to get the maximum value across each sub-key (the first item of each entry's value). To do that, you can use this:

from collections import defaultdict

max_values = defaultdict(lambda: (float('-inf'), None))

for label, text, value in d.values():
    max_values[label] = max(max_values[label], (value, text))

Using defaultdict here with a default value of (float('-inf'), None) allows us to compare new max values to old new values without having to check if a max value was recorded in the first place.

max_values ends up as:

{
    '1': (0.8, 'Toronto'), 
    '2': (0.8871413469314575, 'Arkansas'), 
    '3': (0.8, 'Toronto'), 
    '4': (0.8, 'Turkey'), 
    '5': (0.8, 'Hebron, Kentucky'),
    '6': (0.8, 'Ontario'), 
    '7': (0.9545853137969971, 'London'), 
    '8': (0.8454625606536865, 'UNITED STATES OF AMERICA'),
    '9': (0.8, 'Raleigh–Durham International Airport'), 
    '10': (0.8, 'United States')
}

edited Jul 20 '20 at 05:47

answered Jul 20 '20 at 05:40

Mario Ishac

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this works. but i would like to get the text like Metrolink, Toronto etc having the max values in the max_values. – Jul 20 '20 at 05:43
@Binny Updated answer to include the text, let me know if it works for you. – Mario Ishac Jul 20 '20 at 05:48
Some groups (4, 5, 8, 10) have multiple entries that have equally high value; this method will not list _all_ the entries with the maximum value within the group. – Niko Föhr Jul 20 '20 at 06:16
can i get the text like Toronto,London etc only from the results @Mario Ishac – Jul 20 '20 at 06:26

score 0 · Answer 3 · answered Jul 20 '20 at 05:53

you could get sorted dictionary with following code:

dict(sorted(d.items(), key=lambda kv:(int(kv[1][0]), kv[1][2])))

if you want to sort based on first element and second element, you cloud ues:

dict(sorted(d.items(), key=lambda kv:(int(kv[1][0]), kv[1][1])))

Find out max value from a python dict

3 Answers3

Short explanation