在子列表中查找包含元组的列表中的最小值

Question

I need to find the smallest value in a list. The list has sublists which contains tuples. I need to find the smallest value in all of those tuples, but it can only include the first 3 values. I managed to achieve with the following code, but I want it to look cleaner.

lst = [[(1, 2, 3, 50)], [(0.2, 0.4, 2, 0.1)], [(0.6, 0.8, 1.2, 0.05)]]

def FitScoreSearch3(fitscores):

  fitscores2 = []
  for x in fitscores:
      for y in x:
          for z in y[:3]:
              fitscores2.append(z)

  return min(fitscores2)

The output is 0.2 as it should be. The output can't be 0.05.

Answer 1

Do your sublists always contain just a single tuple? If so,

def FitScoreSearch3(fitscores):
    return min(min(x[0][:3]) for x in fitscores)

If the sublists are allowed to contain several tuples:

def FitScoreSearch3(fitscores):
    return min(min(y[:3]) for x in fitscores for y in x)

In both cases, this swaps your loops for generator expressions. Also, instead of collecting all the numbers into one big list and then do the min() , the above compute the min() first on the tuple (or rather the first 3 elements of the tuple), after which the global minimum value is computed as the min() of all these "sub-min values". As this does not create an additional data structure, it's faster.

Answer 2

min([value for sublist in lst for value in sublist[0][:3]])

Answer 3

In this code lst2 contains all the values of the first 3 elements of each tuple.

lst2 = [ x for sublist in lst for tpl in sublist for x in tpl[:3] ]
print(min(lst2)) # 0.2

Answer 4

You could do something like -

def fitScoreSearch3(fitScores):
    lst = list(map(lambda x: list(x[0][:3]), fitScores))
    minimum = min(list(map(min, lst)))
    return minimum