Sorting and Merging text-files [SOLVED]

[snippsat]

Could it be because the files got spaces in it?

I couple of tips how you troubleshoot this.

def sort_by_int(path):
    print(path)
    print(path.stem)
    # Path has the stem attribute, which is

Bye adding this you see what happen before error.

Test.

>>> f = Path(r'G:\div_code\answer\file_33.txt')
>>> f.stem
'file_33'
>>> f.stem.split('_', maxsplit=1)
['file', '33']
>>> f.stem.split('_', maxsplit=1)[1]
'33'

Make your error.

>>> f = Path(r'G:\div_code\answer\file33.txt')
>>> f.stem
'file33'
>>> f.stem.split('_', maxsplit=1)
['file33']
>>> f.stem.split('_', maxsplit=1)[1]
Traceback (most recent call last):
  File "<interactive input>", line 1, in <module>
IndexError: list index out of range

In your first post all files you show file_1,file_2,file_3,file_10...ect all had a _,then it should work.
With those print() or add repr()(see all like eg space) you will se all files input before the error.

print(repr(path))
print(repr(path.stem))