How to execute Python scripts in Windows?

Question

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

import sys
print sys.argv[1]

If I execute my script by:

python c:/..../blah.py argument

It prints argument but if I execute script by:

blah.py argument

error occurs:

IndexError...

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?

Answer 1

Simply run the command:

C:>python .\file_name.py

Assuming the file name is within same folder and Python has already been added to environment variables.

Answer 2

you should make the default application to handle python files be python.exe.

right click a *.py file, select "Open With" dialog. In there select "python.exe" and check "always use this program for this file type" (something like that).

then your python files will always be run using python.exe

Answer 3

Additionally, if you want to be able to run your python scripts without typing the .py (or .pyw) on the end of the file name, you need to add .PY (or .PY;.PYW) to the list of extensions in the PATHEXT environment variable.

In Windows 7:

right-click on Computer
left-click Properties
left-click Advanced system settings
left-click the Advanced tab
left-click Environment Variables...
under "system variables" scroll down until you see PATHEXT
left-click on PATHEXT to highlight it
left-click Edit...
Edit "Variable value" so that it contains ;.PY (the End key will skip to the end)
left-click OK
left-click OK
left-click OK

Note #1: command-prompt windows won't see the change w/o being closed and reopened.

Note #2: the difference between the .py and .pyw extensions is that the former opens a command prompt when run, and the latter doesn't.

On my computer, I added ;.PY;.PYW as the last (lowest-priority) extensions, so the "before" and "after" values of PATHEXT were:

before: .COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC

after .COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC;.PY;.PYW

Here are some instructive commands:

C:\>echo %pathext%
.COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC;.PY;.PYW

C:\>assoc .py
.py=Python.File

C:\>ftype Python.File
Python.File="C:\Python32\python.exe" "%1" %*

C:\>assoc .pyw
.pyw=Python.NoConFile

C:\>ftype Python.NoConFile
Python.NoConFile="C:\Python32\pythonw.exe" "%1" %*

C:\>type c:\windows\helloworld.py
print("Hello, world!")  # always use a comma for direct address

C:\>helloworld
Hello, world!

C:\>

Answer 4

On Windows,

To run a python module without typing "python",

--> Right click any python(*.py) file

--> Set the open with property to "python.exe"

--> Check the "always use this program for this file type"

--> Append the path of python.exe to variable environment e.g. append C:\Python27 to PATH environment variable.

To Run a python module without typing ".py" extension

--> Edit PATHEXT system variable and append ".PY" extension to the list.

Answer 5

I encountered the same problem but in the context of needing to package my code for Windows users (coming from Linux). My package contains a number of scripts with command line options.

I need these scripts to get installed in the appropriate location on Windows users' machines so that they can invoke them from the command line. As the package is supposedly user-friendly, asking my users to change their registry to run these scripts would be impossible.

I came across a solution that the folks at Continuum use for Python scripts that come with their Anaconda package -- check out your Anaconda/Scripts directory for examples.

For a Python script test, create two files: a test.bat and a test-script.py.

test.bat looks as follows (the .bat files in Anaconda\Scripts call python.exe with a relative path which I adapted for my purposes):

@echo off
set PYFILE=%~f0
set PYFILE=%PYFILE:~0,-4%-script.py
"python.exe" "%PYFILE%" %*

test-script.py is your actual Python script:

import sys
print sys.argv

If you leave these two files in your local directory you can invoke your Python script through the .bat file by doing

test.bat hello world
['C:\\...\\test-scripy.py', 'hello', 'world']

If you copy both files to a location that is on your PATH (such as Anaconda\Scripts) then you can even invoke your script by leaving out the .bat suffix

test hello world
['C:\\...Anaconda\\Scripts\\test-scripy.py', 'hello', 'world']

Disclaimer: I have no idea what's going on and how this works and so would appreciate any explanation.

Answer 6

Found an incredibly useful answer here: How to run different python versions in cmd?

I would suggest using the Python Launcher for Windows utility that introduced was into Python 3.3 a while ago. You can also manually download and install it directly from the author's website for use with earlier versions of Python 2 and 3.

Regardless of how you obtain it, after installation it will have associated itself with all the standard Python file extensions (i.e. .py, .pyw, .pyc, and .pyo files). You'll not only be able to explicitly control which version is used at the command-prompt, but also on a script-by-script basis by adding Linux/Unix-y shebang #!/usr/bin/env pythonX comments at the beginning of your Python scripts.

As J.F. Sebastian suggests, Python Launcher for Windows is the best and default choice for launching different version of Python in Windows. It used to be a third-party tool, but now it is officially supported since Python 3.3.

New in version 3.3.

The Python launcher for Windows is a utility which aids in the location and execution of different Python versions. It allows scripts (or the command-line) to indicate a preference for a specific Python version, and will locate and execute that version.

This is a great tool just use it!