Short code snippet to get a list of files in one directory that don't have corresponding file in another directory using list comprehension and sets. Also gets unique names where multiple files with same 'base' name.

MissingFiles.py

import os
dir1_vars = [f.split('_')[0] for f in os.listdir(dir1) if f.count('Region01')] # files in this directory have repeating base names with '_Region##' at end, this grabs unique file names
state_vars = [f.split('_')[0] for f in os.listdir('L:/Priv/CORFiles/Geospatial_Library/Data/Project/StreamCat/FTP_Staging/StreamCat/States') if f.count('AL')] # files in this directory have repeating base names with state name at end, this grabs unique file names
missing = list(set(hydroregion_vars) - set(state_vars))