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Atlas · Foundations run-program

Hello, little human. I am Atlas. One useful idea is plenty for a beginning. Read the explanation, then explore an example.

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RUN Program

Running a program asks a language tool or executable to perform its instructions; it is separate from editing the file.

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    Beginner field notes

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    • In a shell with an installed command named python3, python3 hello.py starts that interpreter and gives it the saved source file hello.py.
    • Python reads the file named by the command. Editing another tab, or leaving edits unsaved, does not change the source file it opens.
    • If that file contains only print("Hello, human!"), the displayed result is Hello, human!. The saved source and the displayed result are different things.
    See a worked example

    Run the saved greeting

    One reviewed sample, shared across levels. Nothing here runs on your computer.

    Example review recorded 2026-10-07 · version 1.

    Example input · do not paste
    python3 hello.py
    Example output · do not paste
    Hello, human!

    Assumptions: Python 3 is installed as python3, the shell is in the folder containing hello.py, and hello.py contains only print("Hello, human!"). On Windows with the Python launcher installed, use py -3 hello.py instead. The output ends with a newline.

    Sources for this sample

    Visual

    The command starts Python, Python reads hello.py from the supplied path, and the program displays the greeting.

    The reviewed description and complete diagram source are available here.

    Read the complete diagram source

    This is the source for the reviewed diagram, not a command to run.

    flowchart LR
  C["python3 hello.py"] --> I["Start installed interpreter"]
  I --> F["Read saved hello.py"]
  F --> O["Display greeting"]
    Full explanation and primary sources

    Reviewed explanation

    Suppose hello.py is saved in human-lab and contains print("Hello, human!"). From a shell working in that folder, a Python interpreter can read the file and evaluate that print() call. The command combines two things: the interpreter to start and the filename to give it.

    The worked command assumes your installed Python 3 is available as python3. That name is common on macOS and Linux, but it is not universal and Python is not guaranteed to be installed. On Windows installations that provide the Python launcher, py -3 hello.py is an alternative for selecting Python 3. Use the command name supported by your installation; do not paste the shell prompt or a Python >>> prompt into the command.

    If the shell cannot find the interpreter, address installation or command discovery first. If Python cannot open hello.py, check the working directory, complete filename, and saved location. If Python reports a syntax error, compare the source text with the example. These describe different failure stages; none is proof that you are bad at programming.

    Running arbitrary downloaded code can have effects beyond printing a greeting. This example contains only a print() call, uses no credentials or network services, and does not modify your files. The lesson does not execute it automatically in your browser.

    Source collection

    • Python 3.13: Command line and environment

      Used in: Quick notes

      Script and module execution, whole-input parsing, script arguments, import-path initialization, -I, -P, -u and -v options.

    • Visual Studio Code: Basic editing

      Used in: Quick notes

      Unsaved buffers, explicit and automatic saves, Hot Exit, format-on-save, indentation detection, encoding selection and comparison with saved files.

    • Python 3.13: An Informal Introduction to Python

      Used in: Quick notes · Worked example · Lesson text

      Input and output prompt conventions, strings, print output and escape sequences.

      The Python print() call’s displayed string result and prompt conventions.

    • Python 3.13: Using the Python Interpreter

      Used in: Worked example · Lesson text

      Script execution from a filename, distinction from interactive mode, and installation-dependent interpreter names including the Windows launcher.

    • POSIX.1-2024: pwd

      Used in: Worked example · Lesson text

      The working-directory path needed to interpret a simple relative script filename.

    • Python 3.13: Using Python on Windows — Python Launcher

      Used in: Worked example · Lesson text

      The optional Windows launcher accepts -3 to select a core Python 3 installation; this is conditional on an installed launcher/interpreter, not a universal Windows command.

    Notes AI source review · 2026-10-17

    AI source comparison recorded 2026-10-07. Human learner validation is pending.

    Quick quiz · one question

    Find the stage that needs attention

    Sample scenario. Synthetic POSIX-style environment. python3 is installed and discoverable. Only the listed saved script exists, and it is readable valid Python 3. There are no automatic directory changes, aliases, or network/file side effects. No command is actually executed.

    Available interpreter
    python3 is installed and discoverable in this fixture
    Current working directory
    /human-lab
    Saved file: /human-lab/notes/hello.py
    print("Hello, human!")
    Command to predict
    python3 hello.py

    The available interpreter is python3. Predict the command below: does it reach the saved greeting, fail to find the interpreter, or fail to find the requested script?

    Answers stay on this device.

    Sources and exercise scope

    Original synthetic exercise. AI comparison against primary documentation recorded on 2026-10-08; the references above state their scope. Human learner validation has not been run. A result here records this attempt; it does not establish mastery.

    Follow this learning pathLesson 8 of 8

    From project files to a small program

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    Reference notes · file removal and public access

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    Understand what can change

    These reviewed public notes are available to everyone. They do not establish that an operation ran or inspect your files, backups or permissions.

    File removal

    Before deleting files: deleting a file can remove it without putting it in Trash or a recycle bin, and recovery is not guaranteed. Check the intended targets and whether a usable backup or recovery option exists before continuing.

    Sources for this note

    Public access

    Before making a resource public: public read access can let anyone view the exposed content, and public write access can allow changes to data. Check the actual audience, exposed content and allowed operations before continuing. This guidance does not inspect or change your permissions.

    Sources for this note

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