By the end of this lesson
Distinguish writing source code from executing it and recognise a simple Python result.
Before you start
- Lessons 4, 5 and 7; Python 3.12 available.
Three words to know
- Source code
- The text instructions stored in a program file.
- Variable
- A name referring to a value in a program.
- Standard output
- The normal stream where a program prints its result.
1. Write the program
cd "$HOME/openvist-learn"
cat > hello.py <<'PYTHON'
name = "OpenViST"
print(f"Hello, {name}!")
PYTHONWhat you should see · example output
No output is normally printed while the file is written.
name holds a text string. The f-string inserts that value into the message; print sends the message to standard output. The quoted PYTHON marker belongs to Bash and is not part of the .py file.
2. Read, then run
cat hello.pyWhat you should see · example output
name = "OpenViST"
print(f"Hello, {name}!")python3 hello.pyWhat you should see · example output
Hello, OpenViST!
You do not need chmod +x because you explicitly ask python3 to read the file. Typing a script filename alone is a different execution method and is not needed here.
3. Make a controlled edit
cat > hello.py <<'PYTHON'
name = "learner"
print(f"Hello, {name}!")
PYTHON
python3 hello.pyWhat you should see · example output
Hello, learner!
Changing the file changes the next run, not a run that has already finished. Keeping these two actions separate helps when you later update recipes: save the intended version, run it, then inspect its output.
Read an error before changing anything
- No such file: check the folder and filename.
- SyntaxError: inspect the line indicated by Python for missing quotes or parentheses.
- A prompt containing >>> is Python’s interactive interpreter. Use exit() there before running the shell command python3 hello.py.
YOUR TURN
A small check before you continue
Change the greeting to your first name and predict the result before running it. What part of the first block prevents Bash from expanding its body?
Show a suggested answer
The quoted here-document marker makes the body literal. The final Python output should contain the string assigned to name.
Sources and scope
Documentation and examples reviewed 2026-10-18. Provider screens, package versions and output wording can differ. Examples show expected outcomes; they are not a claim that OpenViST connected to your server or verified your setup.