如何在数组列表中查找最大值

Question

I have a very large list of arrays that looks something like this:

'apples': array([1,2,3,4]), 'pears': array([1,2,10,11]),'oranges': array([1,10,10,3])

I want to find the maximum value out of all the arrays. In my short example above it would be 11.

I am struggling to write something that would give me the maximum value for all arrays in the list. Any thoughts would be welcome.

Answer 1

Your list is actually a dictionary, so you can do this:

arr = {'apples': [1,2,3,4], 'pears': [1,2,10,11],'oranges': [1,10,10,3]}
res = max(map(max, arr.values()))
print(res)

Output:

11

You can also do it using the chain function from itertools module:

from itertools import chain

arr = {'apples': [1,2,3,4], 'pears': [1,2,10,11],'oranges': [1,10,10,3]}
res = max(chain(max(i) for i in arr.values()))
print(res)

Output:

11

Answer 2

would this work?

big_dict = {"apple" : list([1,2,3]),
            "pear" : list([4,5,6])}

print max([max(v) for v in big_dict.itervalues()])

Answer 3

From your example given it looks like that's a dictionary rather than a list, anyways for simplicity let's assume that it is a list in the form of:

[[2,3,55],[23,5,63],[2,3,6],[4,6,78], ...]

So what you can do is iterate over the main list and keep the current max value in a variable, and just compare to max of each array and update if greater.

Example

max_value = 0
for l in yourList:
    curr = max(l)
    if curr > max_value:
        max_value = curr
print max_value

This can be easily converted to use dictionary instead of a list, just iterate over each of the items within the dictionary and the logic would be the same (would have to get max() from the value).

Hope this helps!

Answer 4

If your data is in a dictionary variable d, then give this a try

l=[max(d[key]) for key in d.keys()]
print max(l)

Or you can use a one liner

print max([max(d[key]) for key in d.keys()])

Answer 5

你不能直接这样做，尝试形成另一个数组并检查'max（arraylist）'

Answer 6

First create a new list that contains the max values from each dictionary element then get the max of that new list

dict = {"apples" : [1, 2, 8, 4], "fruits": [3,2,6]} 

maxlst = [max(el) for el in dict.values()]
print(max(maxlst))

Answer 7

The more pythonic way for me is to use comprehension dicts :

dictionary = {'apples': np.array([1,2,3,4]), 
'pears': np.array([1,2,10,11]),'oranges': np.array([1,10,10,3])}

In [144]: { k:v.max() for k,v in dictionary.items() }
Out[144]: {'apples': 4, 'oranges': 10, 'pears': 11}

An other easy way is to use pandas :

In [145]: pd.DataFrame(dictionary).max()
Out[145]: 
apples      4
oranges    10
pears      11
dtype: int32

Answer 8

You can have something like below, for large list

obj={'apples': [1,2,3,4], 'pears': [1,2,10,11],'oranges': [1,10,10,3]}

max(sum(obj.values(), []))

11