How to execute Python scripts in Windows?

I have a simple script blah.py (using Python 2):

If I execute my script by:

It prints argument but if I execute script by:

So arguments do not pass to script.

python.exe in PATH. Folder with blah.py also in PATH.
python.exe is default program to execute *.py files.

What is the problem?

9 Answers 9

When you execute a script without typing «python» in front, you need to know two things about how Windows invokes the program. First is to find out what kind of file Windows thinks it is:

Next, you need to know how Windows is executing things with that extension. It’s associated with the file type «Python.File», so this command shows what it will be doing:

So on my machine, when I type «blah.py foo», it will execute this exact command, with no difference in results than if I had typed the full thing myself:

If you type the same thing, including the quotation marks, then you’ll get results identical to when you just type «blah.py foo». Now you’re in a position to figure out the rest of your problem for yourself.

(Or post more helpful information in your question, like actual cut-and-paste copies of what you see in the console. Note that people who do that type of thing get their questions voted up, and they get reputation points, and more people are likely to help them with good answers.)

Brought In From Comments:

Even if assoc and ftype display the correct information, it may happen that the arguments are stripped off. What may help in that case is directly fixing the relevant registry keys for Python. Set the

Likely, previously, %* was missing. Similarly, set

HKEY_CLASSES_ROOT\Applications\python.exe\shell\open\command The registry path may vary, use python26.exe or python.exe or whichever is already in the registry.

HKEY_CLASSES_ROOT\py_auto_file\shell\open\command

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.

How to run a python file/script from sublime text 3 on cmd in windows 10?

I have been searching the internet up and down for a solution to this. I understand there is SublimeREPL which I can easily use to properly run python code in sublime text 3. However, it’s not sufficient for me. I want to run my python file on the cmd from sublime text 3.

There are many reasons for me. The biggest reason is that i need to test my python files often and I don’t want to cramp my sublime text workspace with thousands of tabs. There are several other reasons but at the moment I just want a solution. Almost everywhere on the internet it only talks about SublimeREPL, so I have been unable to find a solution.

I also understand I can use the cmd manually by going to the file directly and running it there, but its a pain in the back to keep switching to cmd and then to sublime text over and over again.

Therefore, I am looking for a neat solution where I can run my python file from sublime text 3 in cmd. Any help is deeply appreciated.

I am using python 3.7.3

1 Answer 1

The rule of thumb for build systems in Sublime Text is that if you can craft a command line that, when executed manually in the terminal/console, will give you the effect that you want (and that command doesn’t require interactive input), then you can turn it into a build system.

In this case, what you want to do is spawn a new cmd window and do something inside of it; the fact that you’re using Sublime is thus not interesting in the grand scheme of knowing how to do that, which might be why your search didn’t turn up any results.

In Windows, you can use a terminal command like cmd /s /c something to tell the Windows cmd.exe that it should execute the command something . In your case you want to use Python to execute a program, so that might look something like the following to get Python to execute my_file.py .

However if you do that in an existing command prompt, the result is just to run the program in the current window; i.e. you’re telling cmd to run a command, but it’s still running in the current window, which is not what you want.

In order to run the program in a new window, you need to use the start command, which launches a new program. The general format of that would be something like this:

That tells start to launch a new instance of cmd , which you’re telling to run the program, so now the Python program is running in its own window.

There are some general issues with this; the biggest one is that as soon as cmd finishes executing the command you give it, it quits. Similarly, Python also quits when the program is finished. The result of that is that as soon as your program is finished, the window immediately vanishes before you can see what it did.

You could add -i to the python command to get it to go interactive, but then you’d have to interact with the internal python REPL in order to get it to quit and close the window, which it sounds like you don’t want to have to take the step to do.

In that case you need to modify the command you give to cmd to get it to also wait until you press a key.

All told, an example of that might look something like the following as a complete sublime-build file:

This is a version of the internal Python.sublime-build modified to extend the command as outlined above. In order for this to work, you need to be able to enter python at a terminal and have it launch the Python interpreter. If that’s not the case you need to adjust your PATH environment variable as appropriate.

If you’re using Python 3, you may need to replace python with python3 or similar in the command so that cmd knows what to execute.