Directory Listing with size (no sub folders) via Python 12

PS E:\> python getDirSize05.py
running on dir "."
Traceback (most recent call last):
  File "getDirSize05.py", line 31, in <module>
    listContents();
  File "getDirSize05.py", line 24, in listContents
    f.write(', ')
TypeError: a bytes-like object is required, not 'str'