Chapter 4 Hello, World!

4.1 Learning objectives

Understand how to run Python scripts from the command line

4.2 Python “Hello, World!” example

Create a new file named 01-helloworld.py using the text editor and write the following code:
```
#!/usr/bin/env python3
print("Hello, World!")
```
- The beginning of the first line, #!, it is called a “hashbang” or “shebang”. That indicates which interpreted should process (Python in this case) the file.
- We use /usr/bin/env to find the Python interpreter in the user’s environment, which is more flexible than specifying a path like /usr/bin/python3. This way, it works regardless of where Python is installed on the system.
- python3 is the interpreter that will run the script. It ensures that the script is executed with Python 3, which is important because Python 2 and Python 3 have different syntax and features.
- Lastly print("Hello, World!") is the actual Python code that prints “Hello, World!” to the terminal.

4.3 Run a Python script

Save the file and make it executable:
```
chmod +x 01-helloworld.py
```
In the terminal, run the script by typing:
```
./01-helloworld.py
```
You should see the output:
```
Hello, World!
```

4.4 Summary

Congratulations! You have just:

Created a Python script that prints “Hello, World!” to the terminal
Made the script executable
Ran the script from the command line