Print the key for the maximum out of data set

Question

Currently my data set is:

{('NSW', '06'): 0.4, ('QLD', '06'): 0.2, ('VIC', '06'): 0.0, ('NSW', '07'): 0.2, ('QLD', '07'): 0.4, ('VIC', '07'): 0.0, ('NSW', '08'): 0.2, ('QLD', '08'): 0.2, ('VIC', '08'): 0.0, ('NSW', '09'): 0.2, ('QLD', '09'): 0.2, ('VIC', '09'): 0.0, ('NSW', '10'): 0.2, ('QLD', '10'): 0.2, ('VIC', '10'): 0.0, ('NSW', '11'): 0.2, ('QLD', '11'): 0.6, ('VIC', '11'): 0.0}

I have achieved this from doing:

key = (state,month)
    if key not in rainfall_and_month:
        rainfall_and_month[key] = rainfall
    if key in rainfall_and_month:
        rainfall_and_month[key] = min(rainfall, rainfall_and_month[key])

I wish to print out the largest value out of the key-value pairs. So basically I would like to make the code find "('QLD', '11'): 0.6", and then print out,

A-value: QLD
B-value: 11

separately, so I would probably end up doing

print("A-value:", state)
print("B-value:", month)

However I'm not sure as to how to find the largest value then extract those data points.

You gotta at least make an attempt and put it up here. – rassa45 May 15 '18 at 04:50 — rassa45, May 15 '18 at 04:50

rassa45 · Answer 1 · 2018-05-15T04:58:50.303

0

In Python 3, dictionaries have a method called .items() which returns a generator of the dictionary items as a tuple of tuples. Python 2 equivalent is .iteritems(). In your case, if the dict is named data_dict

dict_items = data_dict.items()

The max function in Python allows you to enter a lambda function, which basically tells it what value to compare by.

max_item_tuple = max(dict_items, key=lambda currentTuple: currentTuple[1])

Now your max_item_tuple contains the tuple of the key value pair that you need from your dict.

For example, if I had a dictionary of {"something": 1, "nothing": 4, "everything": 3}, my max_item_tuple would become ("nothing", 4).

edited May 15 '18 at 04:58

answered May 15 '18 at 04:52

rassa45

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why the Tuple? sorry – P. Parker May 15 '18 at 04:54
Once I converted the dictionary into items, the key value pairs became key value tuples instead. Check the edited answer. something like `{1: "a"}` will become `[(1, 'a')]`. – rassa45 May 15 '18 at 04:59

score 0 · Answer 2 · answered May 15 '18 at 04:54

0

here is an alternative to lambda:

>>> max_pair = max(data.items(), key=operator.itemgetter(1))
('QLD', '11')
>>> max_pair[0]
'QLD'
>>> max_pair[1]
'11'

answered May 15 '18 at 04:54

Ali Yılmaz

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What is this system of normal brackets called? Since I know square brackets are for lists, curly brackets are for dictionaries, so what are () brackets for? – P. Parker May 15 '18 at 04:57
it's for `tuple`. – Ali Yılmaz May 15 '18 at 04:58
https://www.tutorialspoint.com/python/python_tuples.htm – Ali Yılmaz May 15 '18 at 04:58

score 0 · Answer 3 · answered May 15 '18 at 04:56

Use max to find max of value. It takes a keyword parameter key which can be assigned to value based on what you need to find the maximum of.

Consider using operator module. operator.itemgetter(1) takes the value of each key in every iterations.

import operator

s = {('NSW', '06'): 0.4, ('QLD', '06'): 0.2, ('VIC', '06'): 0.0, ('NSW', '07'): 0.2, ('QLD', '07'): 0.4, ('VIC', '07'): 0.0, ('NSW', '08'): 0.2, ('QLD', '08'): 0.2, ('VIC', '08'): 0.0, ('NSW', '09'): 0.2, ('QLD', '09'): 0.2, ('VIC', '09'): 0.0, ('NSW', '10'): 0.2, ('QLD', '10'): 0.2, ('VIC', '10'): 0.0, ('NSW', '11'): 0.2, ('QLD', '11'): 0.6, ('VIC', '11'): 0.0}

result = max(s.items(), key=operator.itemgetter(1))

A_value = result[0][0]  # QLD
B_value = result[0][1]  # 11

Print the key for the maximum out of data set

3 Answers3