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:
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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.
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Open a prompt (a Windows ‘cmd’ shell that is a text interface into the computer):
start > run > “cmd” (in the little box). OK.
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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
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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.