Scripts and the Terminal

Create a Python script as a plain-text file, find it from the terminal, and run it with a verified interpreter command. Learn how the current working directory, filename, and command determine which source code Python executes.

A Python script is a plain-text file that contains Python code. Saving code in a file lets you inspect it, run it again, and keep it after the terminal closes.

In this lesson, you will create hello.py, place the terminal in the same folder, and ask the Python interpreter to run the file. The complete workflow is:

1. create a folder and a plain-text file;
2. write Python code in the file;
3. confirm that the terminal is looking at the correct folder;
4. run the file with the Python command that worked in the previous lesson;
5. compare the output with the code.

Create a Folder and Script

Use your file manager to create a folder named python-practice. A directory is another name for a folder.

Inside that folder, create a plain-text file named hello.py. The .py extension tells people and software that the file contains Python source code. Enter these two lines:

Save the file. Check that its complete name is hello.py, not hello.py.txt. Some operating systems hide filename extensions, so display the file's details if the complete name is not visible.

You can use any editor that saves plain text. If you use TextEdit on macOS, choose Format → Make Plain Text before saving. If you use Notepad on Windows and it tries to add .txt, choose All files as the file type when saving. A code editor can also save the file, but you do not need to install one for this lesson.

The Current Working Directory

The terminal always has a current working directory: the folder in which it looks for files unless you provide another path. We will place the terminal in python-practice before running hello.py.

Many file managers have an Open in Terminal action for a folder. If yours does, use it on python-practice.

Otherwise, open a terminal and type cd followed by a space. cd means change directory. Drag the python-practice folder into the terminal if your system supports this, then press Enter. Dragging the folder inserts its path, including any characters needed for spaces in folder names.

You can now ask the terminal to print its current location. pwd means print working directory:

pwd

PowerShell also accepts pwd. The printed path should end with python-practice.

Next, list the files in that folder.

On macOS or Linux:

ls

On Windows PowerShell:

dir

The list should contain hello.py. If it does not, either the terminal is looking at a different folder or the file was saved somewhere else. Resolve that difference before running Python.

Run the Script

Use the Python command that printed a suitable version in the previous lesson.

If your command is python3, run:

python3 hello.py

If your command is python, run:

python hello.py

If your command is py, run:

py hello.py

Each command has two parts separated by a space:

• python3, python, or py starts the Python interpreter;
• hello.py is an argument that tells the interpreter which script to run.

Python reads the file from top to bottom. The terminal should show:

Hello from a file
2 + 3 = 5

The source file contains print, quotation marks, parentheses, and the expression 2 + 3. The output contains only the text and values that the two calls to print() display.

When Python Cannot Find the File

Suppose the file is named hello.py, but the command says:

python3 helo.py

The filename is missing an l. Python may report that it cannot open the file. This is a filename or path problem, not a problem with the Python instructions inside the file.

If Python cannot find a script:

1. use pwd to inspect the current working directory;
2. use ls or dir to inspect the filenames there;
3. compare the listed filename with the filename in the run command;
4. correct the folder or spelling, then run the command again.

Read the evidence before reinstalling Python or changing the script's contents. A working interpreter can still receive the wrong file path.

Why Saved Scripts Are Useful

A script keeps the source code between runs. You can close the terminal, return later, and run the same file again. You can also inspect exactly what changed between two runs.

This makes scripts useful for learning, debugging, and repeatable experiments. They are not the only way to work with Python, the next lesson introduces an interactive session for quick calculations but they provide a durable record of a program.

What You Can Now Do

You can create a Python source file, place the terminal in its folder, and run the file with a verified interpreter command. The next lesson starts Python without a script so that you can evaluate small expressions interactively.