Python: Start new command prompt on Windows and wait for it finish/exit

I don’t understand why it’s so hard to do this on Windows.

I want to spawn a bunch of command prompt windows which will run other scripts. The reason I want this is so I can see all the output from each script neatly (if I have them just be threads/subprocesses in the main window I can’t view all the output properly). I also don’t want to log the output because it’s mostly for viewing progress bars, which don’t really work with log files.

So individual parts of my requirements work, but not together:

However, os system won’t let me wait until the command finishes (since start is the actual command, the second it opens the new command prompt it’s «done»)

Similarly if I try:

So how do I do this? I read somewhere that a solution could be to use processgroup but it’s unix only. or something like that

Or if you have a neat way of displaying the output from all the subprocesses in a single window, then I don’t need to open a new command prompt and can simply use threads. That works too, but if I have lets say 4 threads downloading something and displaying a progress bar as well as outputting other information I don’t know how to display that in a way that can be read (as well as avoiding them all colliding with each other).

PS: This is on Windows Vista. PPS: I’d preferably like a solution that works on Windows, Linux and Mac, I’m focusing on Windows for now but I’d like a solution that works for all three, and I know Windows is the most finicky. I would just substitute «the start cmd /c» for the OS appropriate command.

Python to close own CMD shell window on exit

I am running multiple processes (hundreds), each of which is in python and invoked using:

where the /k leaves the cmd window open after execution. This is good to inspect for errors. However, as I call hundreds of jobs, my screen gets cluttered.

How then to make python close its own host cmd window on successful completion only? I need the errored jobs to remain visible.

2 Answers 2

Let us first analyze what the two posted Python script lines really do on execution of the Python script. Thanks goes to eryksun for his deep investigation really using Python resulting in a correct description as it can be read below now.

os.system() results in execution of cmd.exe /C in foreground with a console window and halts execution of the Python script until Windows command interpreter terminates. If the Python script itself is executed in a console, the started cmd.exe inherits this console.

This command process starts with start , an internal command of cmd.exe , one more command process with a foreground console window. Fine, but this second command process terminates immediately on finishing execution of the command. That is not so good if you want to see errors output by the executed script or by Python interpreter itself on running the Python script.

So the second command process starts cmd.exe with option /k to keep running this command process inheriting the console created by start and the console window opened after finishing the execution of the specified command.

The second command process runs internal command call which is not necessary at all because python is in real python.exe , a console application and not a batch file. Therefore call is not needed at all.

It is advisable to always specify applications and scripts with complete name of file, i.e. file name + file extension and not just file name only. If the path to executable/script is known and fixed, it should be specified too. This makes the execution of the application/script independent on what is the current directory and the environment variables PATHEXT and PATH .

Python interpreter executes the specified Python script in second console.

The first command process started with os.system() terminates immediately after start finished which occurs already after starting cmd.exe /k while python.exe is interpreting the Python script.

So remaining is the second command process running the Python interpreter with the script. This command process keeps running even after Python interpreter terminated after finishing execution of specified Python script.

So the goal is to terminate also the second command process with the console window once Python interpreter finished the execution of the Python script, but only if no error occurred on execution of the script.

Well, I don’t have Python installed at all, but I suppose it exits with a return code greater 0 on an error on execution of a script. Otherwise the exit code is 0 on successful execution of the script.

So it might work to use a command like this:

The command line to execute by second command process started with start cmd.exe /K contains two commands now:

1. Python interpreter python.exe with the script to execute as parameter
   and
2. the internal command exit whereby this second command should be executed by Windows command interpreter only if exit code of first command is 0 because of operator && .

See the answer on Single line with multiple commands using Windows batch file for details about single command line with more than one command to execute.

Each ampersand must be escaped here with escape character of Windows command interpreter which is the caret character ^ . This is necessary as otherwise && would be interpreted by first command process running start as additional command to run after successful execution of start .

Please note that I don’t have Python installed and therefore made just following test from within a command prompt window using a batch file Test.bat with the single command line @echo %

dp0 executed. & exit /B 1 .

Test.bat is a batch file and not an executable which requires the usage of command call . The started command process with no specific window title keeps open because Test.bat exits with return code 1. The started command process exits itself if I modify in Test.bat the number 1 to 0 at end of the command line.

Of course it is necessary that the script code itself halts script execution on an error detected by the script code on using this solution.

How to stop Python closing immediately when executed in Microsoft Windows

I have just started college and we are going to be using python. We really have done nothing so I have downloaded the program and done some print commands, and that’s it.

When I run my .py file (a print command) it immediately closes after appearing. I understand why it does this — it’s given the output, so it’s done what it needs to do — but I also understand that you can stop this from happening.

I looked around this website and none of the solutions given to this question worked, either that or I didn’t understand them.

Is there a simple command I can input to my IDLE editor that will put the program on hold or something? I have tried input(«prompt: «) as suggested by someone, and that made no difference.

If there isn’t a command for this, is there a way to change the settings on the computer so that programs don’t auto close?

16 Answers 16

In Python 3, add the following to the end of your code:

This will cause the program to wait for user input, with pressing ENTER causing the program to finish.

You can double click on your script.py file in Windows conveniently this way.

The only thing that worked for me -i command line argument.

Just put all your python code inside a .py file and then run the following command;

It means that if you set -i variable and run your module then python doesn’t exit on SystemExit. Read more at the this link.

Open your cmd (command prompt) and run Python commmands from there. (on Windows go to run or search and type cmd) It should look like this:

This will execute your code in cmd and it will be left open. However to use python command, Python has to be properly installed so cmd recognizes it as a command. Checkout proper installation and variable registration for your OS if this does not happen

Run the command using the windows command prompt from your main Python library source. Example.

at the end to have it stop.

If you just want a delay

Depending on what I’m using it for, or if I’m doing something that others will use, I typically just input(«Do eighteen backflips to continue») if it’s just for me, if others will be using I just create a batch file and pause it after

I use the above if there is going to be files renamed, moved, copied, etc. and my cmd needs to be in the particular folder for things to fall where I want them, otherwise — just

In Python 2.7 adding this to the end of my py file ( if __name__ == ‘__main__’: ) works:

The reason why it is closing is because the program is not running anymore, simply add any sort of loop or input to fix this (or you could just run it through idle.)

I know a simple answer! Open your cmd, the type in: cd C:\directory your file is in and then type python your progam.py

Well I got similar issue, It is solved by adding Environment Variable.

Add System Variables in Window

Your Python path.

I think I am too late to answer this question but anyways here goes nothing.

I have run in to the same problem before and I think there are two alternative solutions you can choose from.

from time import * sleep(10)

1. using a prompt message (note that I am using python 2.7)

exit_now = raw_input(«Do you like to exit now (Y)es (N)o ? «)’

if exit_now.lower() = ‘n’

//more processing here

Alternatively you can use a hybrid of those two methods as well where you can prompt for a message and use sleep(sometime) to delay the window closing as well. choice is yours.

please note the above are just ideas and if you want to use any of those in practice you might have to think about your application logic a bit.

I couldn’t find anywhere on the internet a true non-script specific, double click and the window doesn’t close solution. I guess I’m too lazy to drag and drop or type when I don’t need to so after some experimentation I came up with a solution.

The basic idea is to reassociate .py files so they run a separate initial script before running the intended script. The initial script launches a new command prompt window with the /k parameter which keeps the command prompt open after completion and runs your intended script in the new window.

Maybe there are good reasons not to do this, those with more knowledge please comment if so, but I figure if I run into any it is easy to revert back if needed. One possibly undesirable side effect is dragging and dropping or typing and running from a command prompt now opens a second command prompt rather than running in the command prompt you dragged or typed in.

Python on Windows FAQ¶

How do I run a Python program under Windows?В¶

This is not necessarily a straightforward question. If you are already familiar with running programs from the Windows command line then everything will seem obvious; otherwise, you might need a little more guidance.

Unless you use some sort of integrated development environment, you will end up typing Windows commands into what is variously referred to as a “DOS window” or “Command prompt window”. Usually you can create such a window from your search bar by searching for cmd . You should be able to recognize when you have started such a window because you will see a Windows “command prompt”, which usually looks like this:

The letter may be different, and there might be other things after it, so you might just as easily see something like:

depending on how your computer has been set up and what else you have recently done with it. Once you have started such a window, you are well on the way to running Python programs.

You need to realize that your Python scripts have to be processed by another program called the Python interpreter. The interpreter reads your script, compiles it into bytecodes, and then executes the bytecodes to run your program. So, how do you arrange for the interpreter to handle your Python?

First, you need to make sure that your command window recognises the word “py” as an instruction to start the interpreter. If you have opened a command window, you should try entering the command py and hitting return:

You should then see something like:

You have started the interpreter in “interactive mode”. That means you can enter Python statements or expressions interactively and have them executed or evaluated while you wait. This is one of Python’s strongest features. Check it by entering a few expressions of your choice and seeing the results:

Many people use the interactive mode as a convenient yet highly programmable calculator. When you want to end your interactive Python session, call the exit() function or hold the Ctrl key down while you enter a Z , then hit the “ Enter ” key to get back to your Windows command prompt.

You may also find that you have a Start-menu entry such as Start ‣ Programs ‣ Python 3.x ‣ Python (command line) that results in you seeing the >>> prompt in a new window. If so, the window will disappear after you call the exit() function or enter the Ctrl-Z character; Windows is running a single “python” command in the window, and closes it when you terminate the interpreter.

Now that we know the py command is recognized, you can give your Python script to it. You’ll have to give either an absolute or a relative path to the Python script. Let’s say your Python script is located in your desktop and is named hello.py , and your command prompt is nicely opened in your home directory so you’re seeing something similar to:

So now you’ll ask the py command to give your script to Python by typing py followed by your script path:

How do I make Python scripts executable?В¶

On Windows, the standard Python installer already associates the .py extension with a file type (Python.File) and gives that file type an open command that runs the interpreter ( D:\Program Files\Python\python.exe «%1» %* ). This is enough to make scripts executable from the command prompt as ‘foo.py’. If you’d rather be able to execute the script by simple typing ‘foo’ with no extension you need to add .py to the PATHEXT environment variable.

Why does Python sometimes take so long to start?В¶

Usually Python starts very quickly on Windows, but occasionally there are bug reports that Python suddenly begins to take a long time to start up. This is made even more puzzling because Python will work fine on other Windows systems which appear to be configured identically.

The problem may be caused by a misconfiguration of virus checking software on the problem machine. Some virus scanners have been known to introduce startup overhead of two orders of magnitude when the scanner is configured to monitor all reads from the filesystem. Try checking the configuration of virus scanning software on your systems to ensure that they are indeed configured identically. McAfee, when configured to scan all file system read activity, is a particular offender.

How do I make an executable from a Python script?В¶

See cx_Freeze for a distutils extension that allows you to create console and GUI executables from Python code. py2exe, the most popular extension for building Python 2.x-based executables, does not yet support Python 3 but a version that does is in development.

Is a *.pyd file the same as a DLL?В¶

Yes, .pyd files are dll’s, but there are a few differences. If you have a DLL named foo.pyd , then it must have a function PyInit_foo() . You can then write Python “import foo”, and Python will search for foo.pyd (as well as foo.py, foo.pyc) and if it finds it, will attempt to call PyInit_foo() to initialize it. You do not link your .exe with foo.lib, as that would cause Windows to require the DLL to be present.

Note that the search path for foo.pyd is PYTHONPATH, not the same as the path that Windows uses to search for foo.dll. Also, foo.pyd need not be present to run your program, whereas if you linked your program with a dll, the dll is required. Of course, foo.pyd is required if you want to say import foo . In a DLL, linkage is declared in the source code with __declspec(dllexport) . In a .pyd, linkage is defined in a list of available functions.

How can I embed Python into a Windows application?В¶

Embedding the Python interpreter in a Windows app can be summarized as follows:

Do _not_ build Python into your .exe file directly. On Windows, Python must be a DLL to handle importing modules that are themselves DLL’s. (This is the first key undocumented fact.) Instead, link to python NN .dll ; it is typically installed in C:\Windows\System . NN is the Python version, a number such as “33” for Python 3.3.

You can link to Python in two different ways. Load-time linking means linking against python NN .lib , while run-time linking means linking against python NN .dll . (General note: python NN .lib is the so-called “import lib” corresponding to python NN .dll . It merely defines symbols for the linker.)

Run-time linking greatly simplifies link options; everything happens at run time. Your code must load python NN .dll using the Windows LoadLibraryEx() routine. The code must also use access routines and data in python NN .dll (that is, Python’s C API’s) using pointers obtained by the Windows GetProcAddress() routine. Macros can make using these pointers transparent to any C code that calls routines in Python’s C API.

Borland note: convert python NN .lib to OMF format using Coff2Omf.exe first.

If you use SWIG, it is easy to create a Python “extension module” that will make the app’s data and methods available to Python. SWIG will handle just about all the grungy details for you. The result is C code that you link into your .exe file (!) You do _not_ have to create a DLL file, and this also simplifies linking.

SWIG will create an init function (a C function) whose name depends on the name of the extension module. For example, if the name of the module is leo, the init function will be called initleo(). If you use SWIG shadow classes, as you should, the init function will be called initleoc(). This initializes a mostly hidden helper class used by the shadow class.

The reason you can link the C code in step 2 into your .exe file is that calling the initialization function is equivalent to importing the module into Python! (This is the second key undocumented fact.)

In short, you can use the following code to initialize the Python interpreter with your extension module.

There are two problems with Python’s C API which will become apparent if you use a compiler other than MSVC, the compiler used to build pythonNN.dll.

Problem 1: The so-called “Very High Level” functions that take FILE * arguments will not work in a multi-compiler environment because each compiler’s notion of a struct FILE will be different. From an implementation standpoint these are very _low_ level functions.

Problem 2: SWIG generates the following code when generating wrappers to void functions:

Alas, Py_None is a macro that expands to a reference to a complex data structure called _Py_NoneStruct inside pythonNN.dll. Again, this code will fail in a mult-compiler environment. Replace such code by:

It may be possible to use SWIG’s %typemap command to make the change automatically, though I have not been able to get this to work (I’m a complete SWIG newbie).

Using a Python shell script to put up a Python interpreter window from inside your Windows app is not a good idea; the resulting window will be independent of your app’s windowing system. Rather, you (or the wxPythonWindow class) should create a “native” interpreter window. It is easy to connect that window to the Python interpreter. You can redirect Python’s i/o to _any_ object that supports read and write, so all you need is a Python object (defined in your extension module) that contains read() and write() methods.

How do I keep editors from inserting tabs into my Python source?В¶

The FAQ does not recommend using tabs, and the Python style guide, PEP 8, recommends 4 spaces for distributed Python code; this is also the Emacs python-mode default.

Under any editor, mixing tabs and spaces is a bad idea. MSVC is no different in this respect, and is easily configured to use spaces: Take Tools ‣ Options ‣ Tabs , and for file type “Default” set “Tab size” and “Indent size” to 4, and select the “Insert spaces” radio button.

Python raises IndentationError or TabError if mixed tabs and spaces are causing problems in leading whitespace. You may also run the tabnanny module to check a directory tree in batch mode.

How do I check for a keypress without blocking?В¶

Use the msvcrt module. This is a standard Windows-specific extension module. It defines a function kbhit() which checks whether a keyboard hit is present, and getch() which gets one character without echoing it.