Python Group Then Shuffle Sets

Group sequentially then randomize group placement for TS video segments.

import os,time ,random, shutil
loop_times = 10
mySortArr = []
path = r"D:\\XXX\\ts_files"
for file in os.listdir(path):
    if file.endswith('.ts'):
       mySortArr.append(file)
maxFileNum = 4
def find_all_index(arr, item):
    return [i for i, a in enumerate(arr) if a == item]
randomListMax = len(mySortArr)*100
def sortA(filelist):
    tempGroupList = []
    groupList = []
    tempGroupAppendIndex=0
    while tempGroupAppendIndex < randomListMax+1:
      groupList.append(0)
      tempGroupAppendIndex += 1
    i = 0
    countNum = 0
    for files in filelist:
        i += 1
        countNum +=1
        tempGroupList.append(files)
        randomIndex = random.randint(0,randomListMax)
        while groupList[randomIndex] != 0:
          randomIndex = random.randint(0,randomListMax)
        if countNum >= maxFileNum:
             countNum = 0
             rIndex = 0
             for tempItem in tempGroupList:
                  rIndex+=1
                  groupList[randomIndex+rIndex] = tempItem
             for tempItem in reversed(tempGroupList):
                  groupList[randomIndex+rIndex+len(tempGroupList)] = tempItem
                  rIndex+=1
             tempGroupList = []
    listRes = [g for g in groupList if g != 0]
    return listRes
mySortArr = sortA(mySortArr)
for i in range(1, loop_times + 1):
  with open(f"{i}.txt", 'w', encoding='utf-8') as f:
    for content in mySortArr:
        f.write(f"file '{content}'\n")
os.system('copy /B ?*.txt output.txt')
os.system('ffmpeg -f concat -safe 0 -i output.txt -c copy merged.mp4')
for i in range(1, loop_times + 1):
    os.remove(f"{i}.txt")
os.remove('output.txt')
for filename in os.listdir('.'):
    if filename.endswith('.ts'):
        os.remove(filename)
for foldername in os.listdir('.'):
    if foldername.startswith('images_'):
        shutil.rmtree(foldername)