How do I run a Python program in the Command Prompt in Windows 7?

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.

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).

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.

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?

23 Answers 23

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+:

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

Assuming you have Python2.7 installed

Goto the Start Menu

Right Click «Computer»

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 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. http://docs.python.org/3/whatsnew/3.3.html ]

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»):

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.

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).

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.

Associating Python with .py and .pyc

Verify that double-clicking on ApplyRE.py runs it. (It should also have a Python logo as its icon and be labeled «Python File», by the way.) If this isn’t already done, right-click on a .py file, choose Open With, Choose Program, and check «Always use. » This association improves convenience but isn’t strictly necessary—you can specify «python» every time you want to run a script, like this:

Here’s a very specific variation, which is optional unless you need to specify a different version of the interpreter.

But that’s a pain. Fortunately, once Python is installed, in the PATH, and associated with .py, then double-clicking a .py file or directly typing it as a command should work fine. Here, we seem to be running the script directly—it’s nice and simple to run it on a sample file that’s located in the «my scripts» folder along with the script.

Omitting the .py extension (editing PATHEXT)

To further reduce typing, you can tell Windows that .py (and perhaps .pyc files) are executable. To do this, right-click Computer and choose Properties, Advanced, Environment Variables, System Variables. Append «;.PY;.PYC» (without quotes) to the existing PATHEXT variable, or else create it if you’re certan it doesn’t exist yet. Close and reopen the command prompt. You should now be able to omit the .py (FYI, doing so would cause ApplyRE.exe or ApplyRE.bat to run instead, if one existed).

Adding scripts to the system PATH

If you’re going to use your scripts often from the command prompt (it’s less important if doing so via using BAT files), then you’ll want to add your scripts’ folder to the system PATH. (Next to PATHEXT you should see a PATH variable; append «;D:\my scripts» to it, without quotes.) This way you can run a script from some other location against the files in current location, like this:

Success! That’s pretty much all you need to do to streamline the command-line.

Running directly without tweaking the PATH

If you’re a fast typist or don’t mind creating a batch file for each situation, you can specify full paths (for the script, or for the parameters) instead of tweaking PATH.

Creating shortcuts or batch files

If .py is associated with an installed Python, you can just double-click ApplyRE.py to run it, but the console may appear and disappear too quickly to read its output (or failure!). And to pass parameters, you’d need to first do one of the following. (a) Right-click and create a shortcut. Right-click the shortcut to edit properties and append parameters to Target. (b) Create a batch file—a plain text file with a distinct name such as ApplyRErun.bat. This option is probably better because you can ask it to pause so you can see the output. Here is a sample BAT file’s contents, written to be located and run from c:\some files .

Advanced: appending to PYTHONPATH

This usually isn’t necessary, but one other environment variable that may be relevant is PYTHONPATH. If we were to append d:\my scripts to that variable, then other Python scripts in other locations could make use of those via import statements.

Python comes with a script that takes care of setting up the windows path file for you.

After installation, open command prompt

Go to the directory you installed Python in

Run python and the win_add2path.py script in Tools\Scripts

Now you can use python as a command anywhere.

You have to put the python path in the PATH variable.

In the System Variables section, you should have User Variables and System Variables. Search for the PATH variable and edit its value, adding at the end ;C:\python27 .

The ; is to tell the variable to add a new path to this value, and the rest, is just to tell which path that is.

On the other hand, you can use ;%python% to add the variable you created.

You don’t add any variables to the System Variables. You take the existing ‘Path’ system variable, and modify it by adding a semi-colon after, then c:\Python27

So after 30 min of R&D i realized that after setup the PATH at environment variable

C:> cd Python27 C:\ Python27> python.exe

USE python.exe with extension

alternative option is :

if the software is installed properly directly run Python program, your command line screen will automatically appear without cmd.

Go to the Start Menu

Right Click «Computer»

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» or if it says error type «py» instead of «python»

Even after going through many posts, it took several hours to figure out the problem. Here is the detailed approach written in simple language to run python via command line in windows.

1. Download executable file from python.org
Choose the latest version and download Windows-executable installer. Execute the downloaded file and let installation complete.

2. Ensure the file is downloaded in some administrator folder

1. Search file location of Python application.
2. Right click on the .exe file and navigate to its properties. Check if it is of the form, «C:\Users. «. If NO, you are good to go and jump to step 3. Otherwise, clone the Python37 or whatever version you downloaded to one of these locations, «C:\», «C:\Program Files», «C:\Program Files (x86)».

3. Update the system PATH variable This is the most crucial step and there are two ways to do this:- (Follow the second one preferably)

1. MANUALLY
— Search for ‘Edit the system Environment Variables’ in the search bar.(WINDOWS 10)
— In the System Properties dialog, navigate to «Environment Variables».
— In the Environment Variables dialog look for «Path» under the System Variables window. (# Ensure to click on Path under bottom window named System Variables and not under user variables)
— Edit the Path Variable by adding location of Python37/ PythonXX folder. I added following line:-
» ;C:\Program Files (x86)\Python37;C:\Program Files (x86)\Python37\Scripts »
— Click Ok and close the dialogs.

Python 3 installation on windows running from command line

Just curious, is there a particular reason why Python 3.x is not installed on Windows to run default with the command line «python3», like it does on Mac OSX and Linux? Is there some kind of way to configure Python so that it runs like this? Thanks.

EDIT: Just to add, the reason I am asking is because I have both the Python 2 and 3 interpreter installed on my computer, and so it is ambiguous, as both are run using the command «python».

4 Answers 4

the reason I am asking is because I have both the Python 2 and 3 interpreter installed on my computer, and so it is ambiguous, as both are run using the command «python».

To run Python 2 executable:

To run Python 3 executable:

where py is a Python launcher that is bundled with your Python 3 installation.

py recognizes the shebang (e.g., #!/usr/bin/env python3 causes Python 3 executable to be run), it respects virtualenv (if you run py without specifying the explicit python executable version) i.e., run:

and the correct python version is used automatically — you don’t need to specify the Python version on the command-line explicitly.

is there a particular reason why Python 3.x is not installed on Windows to run default with the command line «python3», like it does on Mac OSX and Linux?

OSX and Linux have python executable installed by default as a rule and it refers to Python 2 version in most cases at the moment that is why you need a separate python3 name there.

There is no Python on Windows by default. And therefore any version that you’ve installed is just python (I guess). The recommended way to manage multiple python versions is to use the Python launcher.

Is there some kind of way to configure Python so that it runs like this?

How to run cmd.exe commands from python?

I would like to run to run a script that opens GUI in which i press a start button which runs (opens, writes, runs) cmd.exe command line.

Command is following : «ConverterApp.exe» file1.x file1.y

ConverterApp is placed in a random desktop folder. What is does it converts one type of photo to another. And right now i have to use the command above for every photo, so i want to write pyhton program which will convert all .x files in folder to .y.

From my reaserch on the topic i have to use subprocess , bit im kind of lost on how to use it.

3 Answers 3

use the subprocess module.

you can still use subprocess.call , but for Python versions >3.4, it’s preferred to use the newer subprocess.run .

Note: in both subprocess.call , and subprocess.run , your command should be passed as a sequence (i.e. a list).

Have you looked into using os.system to execute commands? It is simple to use and may be sufficient to accomplish what you are trying to do. On Windows, it usually runs cmd.exe for you.

Execute the command (a string) in a subshell. This is implemented by calling the Standard C function system(), and has the same limitations. Changes to sys.stdin, etc. are not reflected in the environment of the executed command. If command generates any output, it will be sent to the interpreter standard output stream.

On Unix, the return value is the exit status of the process encoded in the format specified for wait(). Note that POSIX does not specify the meaning of the return value of the C system() function, so the return value of the Python function is system-dependent.

On Windows, the return value is that returned by the system shell after running command. The shell is given by the Windows environment variable COMSPEC: it is usually cmd.exe, which returns the exit status of the command run; on systems using a non-native shell, consult your shell documentation.

The subprocess module provides more powerful facilities for spawning new processes and retrieving their results; using that module is preferable to using this function. See the Replacing Older Functions with the subprocess Module section in the subprocess documentation for some helpful recipes.