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Main guard

As explained in Practices of the Python Pro

A main guard is a conditional Python module entry-point idiom that runs code only when the file is executed directly rather than imported.

A main guard is a Python entry-point pattern that runs application code when a file is executed directly, while preventing that code from running during import. This keeps command-line startup behavior explicit and avoids unintended execution. section 6.3.3

A minimal command-line entry point

if __name__ == '__main__': print('Welcome to Bark!') Place startup actions inside the guard, such as initializing a database or starting the application's loop. section 6.3.3

if __name__ == '__main__':
    print('Welcome to Bark!')

Shows the smallest practical form of the main guard and its direct-execution behavior. section 6.3.3

Use the guarded block to assemble the command-line application progressively:

  • Initialize required resources, such as creating the bookmarks table. section 6.3.3
  • Define menus and commands outside or inside the startup flow as appropriate, then call the presentation loop from the guard. section 6.3.3

How Practices of the Python Pro covers it

How deep it goes
Defines the idiom and demonstrates startup actions, but does not explain Python name-binding internals.
Examples
Uses a greeting, database-table initialization, menu construction, and an interactive application loop.
What it assumes
Assumes basic Python modules and imports while teaching the entry-point pattern through a small command-line application.
What you can do after
Build it from scratch by placing Python command-line startup actions inside a main guard.
How it connects
Connects the presentation layer with command-line applications, imports, business logic, persistence, and separation of concerns.
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