Several ways.

• From the shell

  python someFile.py
  

• From inside IDLE, hit F5.

• If you're typing interactively, try this (Python3):

  >>> exec(open("filename.py").read())
  

• For Python 2:

  >>> variables= {}
  >>> execfile( "someFile.py", variables )
  >>> print variables # globals from the someFile module
  

I'm very glad you asked! I was just working on explaining this very thing in our wikibook (which is obviously incomplete). We're working with Python novices, and had to help a few through exactly what you're asking!

Command-line Python in Windows:

1. Save your python code file somewhere, using "Save" or "Save as" in your editor. Lets call it 'first.py' in some folder, like "pyscripts" that you make on your Desktop.

2. Open a prompt (a Windows 'cmd' shell that is a text interface into the computer):

   start > run > "cmd" (in the little box). OK.

3. Navigate to where your python file is, using the commands 'cd' (change directory) and 'dir' (to show files in the directory, to verify your head). For our example something like,

   > cd C:\Documents and Settings\Gregg\Desktop\pyscripts

4. try:

   > python first.py

If you get this message:

'python' is not recognized as an internal or external command, operable program or batch file.

then python (the interpreter program that can translate Python into 'computer instructions') isn't on your path (see Putting Python in Your Path below). Then try calling it like this (assuming Python2.6, installed in the usual location):

> C:\Python26\python.exe first.py

(Advanced users: instead of first.py, you could write out first.py's full path of C:\Documents and Settings\Gregg\Desktop\pyscripts\first.py)

Putting Python In Your Path

Windows

In order to run programs, your operating system looks in various places, and tries to match the name of the program / command you typed with some programs along the way.

In windows:

control panel > system > advanced > |Environmental Variables| > system variables -> Path

this needs to include: C:\Python26; (or equivalent). If you put it at the front, it will be the first place looked. You can also add it at the end, which is possibly saner.

Then restart your prompt, and try typing 'python'. If it all worked, you should get a ">>>" prompt.

There's two things needed.

1. A script must have #! line telling the OS which interpreter to use. In your case your very first line in the code must be #!/usr/bin/env python3

2. You need to open file manager , go to Edit -> Preferences -> Behavior, and select what to do with executable files

   

   3. Finally , make sure your file itself actually has executable permissions set. In terminal you can do chmod +x /path/to/script.py and in GUI, right click on the file and alter its Properties -> Permissions

   

   

The very first line is called shebang line and must start with #! ; whatever comes next is the name of the interpreter that will read your code. In case you are using python3 you could use either #!/usr/bin/python3 or #!/usr/bin/env python3 for portability. If you are not using code that will be specific to python version - just use #!/usr/bin/env python

Note on the script output:

If your script prints output to console, it will need to have terminal window, or alternatively use GUI dialogs such as zenity. Prefer using Run in Terminal option if you want to see the code. If you want the script to do something without seeing console output - use Run option.

In addition, if you have command line parameters , such as sys.argv[1] in the script , you can't set them unless you have terminal window open.

Option 1: Call the interpreter

• For Python 2: python <filename>.py
• For Python 3: python3 <filename>.py

Option 2: Let the script call the interpreter

1. Make sure the first line of your file has #!/usr/bin/env python.
2. Make it executable - chmod +x <filename>.py.
3. And run it as ./<filename>.py