Python find max in list of lists and elements with undefined number of integers and floats

Question

I have a big list of list. I am trying to find max and min in it. Previous questions on this consists lists with strings and this question is differen.t

    big_list = [[137.83,81.80,198.56],0.0,[200.37,151.55,165.26, 211.84],
 0.0,[1,2,3],4,[5,6,0,5,7,8],0,[2,1,4,5],[9,1,-2]]

My code:

max =  max(list(map(max,boxs_list)))

Present output:

TypeError: 'numpy.float64' object is not iterable

Are you expecting to find max = 9 and min =-1 from the list you provided ? — tomgalpin, Jan 30 '20 at 15:47
Also, you say you have a big list of lists but your example is a "big" list of lists and integers — tomgalpin, Jan 30 '20 at 15:48
Does this answer your question? [Flatten an irregular list of lists](https://stackoverflow.com/questions/2158395/flatten-an-irregular-list-of-lists) — wwii, Jan 30 '20 at 15:55

score 2 · Answer 1 · answered Jan 30 '20 at 15:51

You could do the following, using max() and min() with generator expressions, and a check with isinstance() to see if each element is a list or not.

>>> min(sl if not isinstance(sl, list) else min(sl) for sl in big_list)
-2
>>> max(sl if not isinstance(sl, list) else max(sl) for sl in big_list)
9

ansev · Accepted Answer · 2020-01-30T18:44:00.497

1

the problem is that you need the list to contain only lists

np.max(np.concatenate([l if isinstance(l,list) else [l] for l in big_list]))

or

max(map(max,[l if isinstance(l,list) else [l] for l in big_list]))

Output

EDIT: get len of sublist

lens = [len(l) if isinstance(l,list) else 1 for l in big_list]
#[3, 1, 4, 1, 3, 1, 6, 1, 4, 3]

if you only want consider list:

#lens = [len(l) if isinstance(l,list) else None for l in big_list]
#[3, None, 4, None, 3, None, 6, None, 4, 3]

We could do as when we got the max:

list(map(len,[l if isinstance(l,list) else [l] for l in big_list]))
#[3, 1, 4, 1, 3, 1, 6, 1, 4, 3]

I think the best way is:

list(map(lambda x: len(x) if isinstance(x,list) else None ,big_list))
#[3, None, 4, None, 3, None, 6, None, 4, 3]

edited Jan 30 '20 at 18:44

answered Jan 30 '20 at 15:53

ansev

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I liked your online code: `np.max(np.concatenate([l if isinstance(l,list) else [l] for l in big_list]))`. This works fine. Do above `concatenate` work better? – Mainland Jan 30 '20 at 15:59
It depends on the specific case but I think that the best map works here – ansev Jan 30 '20 at 16:00
My `big_list' also has elements. Does your code considers only lists of list? or it considers all values inside that list? – Mainland Jan 30 '20 at 16:02
`max(map(max,[l if isinstance(l,list) else [l] for l in big_list]))` you don't need `list` here:) – ansev Jan 30 '20 at 16:02
it consider all values – ansev Jan 30 '20 at 16:04
In above question, how to find length of each sublist? – Mainland Jan 30 '20 at 16:42
If there is no list but there is a value, is the length 1? – ansev Jan 30 '20 at 18:40
I submitted a new question on this: https://stackoverflow.com/questions/59990774/python-find-size-of-each-sublist-in-a-list/59990915#59990915 – Mainland Jan 30 '20 at 18:55

Python find max in list of lists and elements with undefined number of integers and floats

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