How Do I Run a Python Program in the Command Prompt in Windows 7?

Question

I'm trying to figure out how to run Python programs with the Command Prompt on Windows 7. (I should have figured this out by now...)

When I typed "python" into the command prompt, I got the following error:

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

The first place I found when looking for help was this site: .

It was somewhat helpful, but the tutorial was written for Windows 2000 and older, so it was minimally helpful for my Windows 7 machine. I attempted the following:

For older versions of Windows the easiest way to do this is to edit the C:\AUTOEXEC.BAT >file. You would want to add a line like the following to AUTOEXEC.BAT:

This file did not exist on my machine (unless I'm mistaken).

Next, I tried this: (here: How do I run a Python program?)

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.

This was relevant enough for Windows 7, and I made my way to the System Variables. I added a variable "python" with the value "C:\Python27"

I continued to get the error, even after restarting my computer.

Anyone know how to fix this?

Accepted Answer

You need to add C:\Python27 to your system PATH variable, not a new variable named "python".

Find the system PATH environment variable, and append to it a ; (which is the delimiter) and the path to the directory containing python.exe (e.g. C:\Python27). See below for exact steps.

The PATH environment variable lists all the locations that Windows (and cmd.exe) will check when given the name of a command, e.g. "python" (it also uses the PATHEXT variable for a list of executable file extensions to try). The first executable file it finds on the PATH with that name is the one it starts.

Note that after changing this variable, there is no need to restart Windows, but only new instances of cmd.exe will have the updated PATH. You can type set PATH at the command prompt to see what the current value is.

Exact steps for adding Python to the path on Windows 7+:

Computer -> System Properties (or Win+Break) -> Advanced System Settings
Click the Environment variables... button (in the Advanced tab)
Edit PATH and append ;C:\Python27 to the end (substitute your Python version)
Click OK. Note that changes to the PATH are only reflected in command prompts opened after the change took place.

Answer 2

Assuming you have Python2.7 installed

Goto the Start Menu
Right Click "Computer"
Select "Properties"
A dialog should pop up with a link on the left called "Advanced system settings". Click it.
In the System Properties dialog, click the button called "Environment Variables".
In the Environment Variables dialog look for "Path" under the System Variables window.
Add ";C:\Python27" to the end of it. The semicolon is the path separator on windows.
Click Ok and close the dialogs.
Now open up a new command prompt and type "python"

It should work.

Answer 3

It has taken me some effort looking for answers here, on the web, and and in the Python documentation, and testing on my own, to finally get my Python scripts working smoothly on my Windows machines (WinXP and Win7). So, I just blogged about it and am pasting that below in case it's useful to others. Sorry it's long, and feel free to improve it; I'm no expert.

[UPDATE: Python 3.3 now includes the Python Launcher for Windows, which allows you to type py (rather than python) to invoke the default interpreter, or py -2, py -3, py -2.7, etc. It also supports shebang lines, allowing the script itself to specify. For versions prior to 3.3, the launcher is available as a separate download. ]

Running Python scripts conveniently under Windows

Maybe you're creating your own Python scripts, or maybe someone has given you one for doing something with your data files. Say you've acquired a Python script and have saved it to "D:\my scripts\ApplyRE.py". You want to run it conveniently by either double-clicking it or typing it into the command line from any location, with the option of passing parameters to it like this (-o means "overwrite the output file if it already exists"):

ApplyRE infile.txt outfile.txt -o

Say you also have a data file, "C:\some files\some lexicon.txt". The simplest option is to move the file or the script so they're in the same location, but that can get messy, so let's assume that they'll stay separate.

Must Read

Making sure Windows can find the Python interpreter

After installing Python, verify that typing python into a command prompt works (and then type exit() to get back out of the Python interpreter).

C:\>python
Python 3.2 (r32:88445, Feb 20 2011, 21:29:02) [MSC v.1500 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> exit()
C:\>

If this doesn't work, you'll need to append something like ";C:\Python32" (without quotes) to the PATH environment variable. See PATHEXT below for instructions.

How Do I Run a Python Program in the Command Prompt in Windows 7?

24 Answers

Running Python scripts conveniently under Windows

Must Read

Making sure Windows can find the Python interpreter

Sophia Al-Mansoor