嵌套for循环的简化

Question

此代码有效，但我相信它可以变得更简单，还允许包含额外的部分，而无需向嵌套循环添加行的所有麻烦。怎么样？

#---------------------------------------------------------------------------        ----
# Name:        TotalweightCombination
# Purpose:      Combine weight/length/etc of pieces to get a sum as close as possible to optSum. Maximally 6 pieces allowed in the resulting combination. 
#-------------------------------------------------------------------------------

pieces=[31.75,12.5,28.9,20.95,31.5,13.8,13.95,11.2,32.9,16.6,8.6,17.85]

print("Sum weight pieces:",sum(pieces))
numpieces=len(pieces)
pieces.append(0)   # We include a piece with weight 0 to allow combinations with fewer than 6 pieces
optSum=142
bestDiff=1000
totCheck=0

for i,iv in enumerate(pieces):
    for j,jv in enumerate(pieces):
        if jv==0 or j!=i:
            for k,kv in enumerate(pieces):
                if kv==0 or k not in [i,j]:
                    for l,lv in enumerate(pieces):
                        if lv==0 or l not in [i,j,k]:
                            for m,mv in enumerate(pieces):
                                if mv==0 or m not in [i,j,k,l]:
                                    for n,nv in enumerate(pieces):
                                        if nv==0 or n not in [i,j,k,l,m]:
                                            totCheck+=1
                                            theList=[iv,jv,kv,lv,mv,nv]
                                            diff=abs(sum(theList)-optSum)
                                            if diff<bestDiff:
                                                bestDiff=diff
                                                chosen=theList
                                                print("New best sum: %s with "%sum(chosen),chosen)

theTotal=sum(chosen)
print("We try to obtain the sum %s with %s pieces. Checked %s combinations. Best combination: %s gives theTotal %s. Deviation %.4f%%."%(optSum,numpieces,totCheck,[i for i in chosen if i!=0],theTotal,100*(theTotal/optSum-1)))

（编辑：更正了一些制表符错误）

Answer 1

你应该使用 combinations() from itertools 模块。

from itertools import combinations

for theList in combinations(pieces, 6)):
   # theList stands here for exactly the same as in your most inner loop. 
   # Do whatever you want with it here

嵌套for循环的简化

Simplification of nested for loop

python

for-loop

nested-loops

simplification