How to Run a Python Script via a File

Before writing Python scripts, you should be able to run them. If you run a Python script, Python makes sure the computer understands the code: it interprets.

Any Python script should end with the .py extension. So program names could be:

• hello.py
• world.py
• sort_names.py

The way to execute Python differs on systems (Linux,Mac,Windows), but comes down to the same idea. Any script will do, you can use the hello world script.

Windows

On Windows, you likely installed Python in C:\Python..\python.exe
But your program is most probably somewhere else, like on your desktop.
First open a command prompt (Win+R, cmd or command.exe)
You can run it with this command:

C:\Python35\python.exe C:\Users\Username\Desktop\my_python_script.py

On older versions of windows, Python is not installed by default. If that's the case, install it first.

On Mac OS X or Linux

If you use Apple Mac or Linux, Python is often installed by default. On top of the program, you can add one of these lines:

#!/usr/bin/env python

or

#!/usr/bin/env python3

This defines that you want to use Python environment. Save your file (hello.py).

Then in the command line, make it executable:

chmod +x hello.py

Then you can run it like any other program. An alternative is to run it with the python interpreter:

    python hello.py

Alternatives

Working from the command line can be quite challenging. For a single file you can do it, but for larger apps this gets cumbersome.

Most developers use an app to develop, a so called IDE. This lets you work with multiple files easily, run with a keyboard shortcut and other simplifications.

Sometimes people work directly in the Python shell, sometimes named REPL. This lets you interact with Python, but doesn't require a file.

To open the Python shell, you simply type 'python' in the command prompt. That sets you into the shell.

➜  ~ python3
Python 3.7.5 (default, Nov 20 2019, 09:21:52) 
[GCC 9.2.1 20191008] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> 

To exit the shell, press Ctrl+Z.

Related links:

• Python language homepage
• Python tutorial