如何修改迭代列表？

Question

Following scenario of traversing dir structure.

"Build complete dir tree with files but if files in single dir are similar in name list only single entity"

Example tree ( let's assume they're are not sorted ):

    - rootDir
        -dirA
            fileA_01
            fileA_03
            fileA_05
            fileA_06
            fileA_04
            fileA_02
            fileA_...
            fileAB
            fileAC
        -dirB
            fileBA
            fileBB
            fileBC

Expected output:

    - rootDir
        -dirA
            fileA_01 - fileA_06 ...
            fileAB
            fileAC
        -dirB
            fileBA
            fileBB
            fileBC

So I did already simple def findSimilarNames that for fileA_01 (or any fileA_ ) will return list [ fileA_01 ... fileA_06 ]

Now I'm in os.walk and I'm doing loop over files so every file will be checked against similar filenames so eg fileA_03 I've got rest of them [ fileA_01 - fileA_06 ] and now I want to modify the list that I iterate over to just skip items from findSimilarNames , without need of using another loop or if 's inside.

I searched here and people are suggesting avoidance of modifying iteration list, but doing so I would avoid every file iteration.

Pseudo code:

for root,dirs,files in os.walk( path ):
    for file in files:
        similarList = findSimilarNames( file )

        #OVERWRITE ITERATION LIST SOMEHOW
        files = (set(files)-set(similarList))

        #DEAL WITH ELEMENT

What I'm trying to avoid is below - checking each file because maybe it's already found by findSimilarNames .

for root,dirs,files in os.walk( path ):
    filteredbysimilar = files[:]
    for file in files:
        similar = findSimilarNames( file )
        filteredbysimilar = list(set(filteredbysimilar)-set(similar))
    #--
    for filteredFile in filteredbysimilar:
        #DEAL WITH ELEMENT

Answer 1

#OVERWRITE ITERATION LIST SOMEHOW

You can get this effect by using a while-loop style iteration. Since you want to do set subtraction to remove the similar groups anyway, the natural approach is to start with a set of all the filenames, and repeatedly remove groups until nothing is left. Thus:

unprocessed = set(files)
while unprocessed:
    f = unprocessed.pop() # removes and returns an arbitrary element
    group = findSimilarNames(f)
    unprocessed -= group # it is not an error that `f` has already been removed.
    doSomethingWith(group) # i.e., "DEAL WITH ELEMENT" :)

Answer 2

How about building up a list of files that aren't similar?

unsimilar = set()
for f in files:
    if len(findSimilarNames(f).intersection(unsimilar))==0:
        unsimilar.add(f)

This assumes findSimilarNames yields a set.