listdir

[Smith]

Hello to all,
I wanted to know because even though the files are present on the 
directory I write input gives me "file not found".
You can help me?
Thank you

a = input("Digita la directory dove vuoi trovare i file py:  ")
for file in os.listdir(a):
     if file.endswith(".py"):
         print(file)
     else:
         break
print("File not found")