How to search full path of specified file

[Gribouillis]

Why not use the user-friendly pathlib module from the standard library ?

from pathlib import Path

file1_name = Path("D:") / "Backupdata"
post_fix = Path() / "PythonCodes" / "InputCSV1.csv"

if (file1_name / post_fix).isfile():
    print("File exists")
else:
    print("No such file")