The day I realized the shebang matters

A developer found that execute permission alone is not enough to run a Python file directly from the shell.

The script failed with “Permission denied” because it was missing a valid shebang line.

Adding the correct interpreter path, such as /usr/bin/env python3 or /usr/bin/python3, fixed the issue.

The lesson: the kernel needs a proper interpreter line to launch executable scripts reliably.