Step 1: Understand Python files.
Python programs are saved as script files so that they can be executed by the Python interpreter.
Step 2: Analyze the options.
(A) .py is the standard extension for Python scripts.
(B) .pt is not a standard Python extension.
(C) .java is used for Java programs.
(D) .exe is an executable file, not a script file.
Step 3: Conclusion.
Therefore, Python script files use the extension .py.