python store a split list into multiple files and items in same line

Question

I have a huge list with 9000 items. I already referred this post here and here. Don't mark it as duplicate

Mylist = [1234,45678,2314,65474,412,87986,21321,4324,68768,1133,712421,12132,0898]

I would like to split my list and store the output of each list in a notepad file

For ex: I wish each of my output list to contain ~10% of items from the original Mylist

So, I tried the below

for k,g in itertools.groupby(Mylist, lambda x: x/10):
      with open("part1.txt", 'w') as file:
      file.write('\n'.join(yourList))

I expect my output to have multiple text files like below and each file should contain 10% of items stored like below in screenshot from original list

part1.txt
part2.txt
part3.txt
part4.txt