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Running a Python script with and without "python" [duplicate]

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?

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:
C:\>assoc .py
.py=Python.File
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:
C:\>ftype Python.File
Python.File="c:\python26\python.exe" "%1" %*
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:
"c:\python26\python.exe" "blah.py" foo
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
HKEY_CLASSES_ROOT\Applications\python26.exe\shell\open\command
key to:
"C:\Python26\python26.exe" "%1" %*
Likely, previously, %* was missing. Similarly, set
HKEY_CLASSES_ROOT\py_auto_file\shell\open\command
to the same value. See http://eli.thegreenplace.net/2010/12/14/problem-passing-arguments-to-python-scripts-on-windows/
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

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

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:\>

How to execute Python scripts in Windows?
You could install pylauncher. It is used to launch .py, .pyw, .pyc, .pyo files and supports multiple Python installations:
T\:> blah.py argument
You can run your Python script without specifying .py extension if you have .py, .pyw in PATHEXT environment variable:
T:\> blah argument
It adds support for shebang (#! header line) to select desired Python version on Windows if you have multiple versions installed. You could use *nix-compatible syntax #! /usr/bin/env python.
You can specify version explicitly e.g., to run using the latest installed Python 3 version:
T:\> py -3 blah.py argument
It should also fix your sys.argv issue as a side-effect.

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.

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.

Can you execute python.exe from any map?
If you do not, chek if you have proper values for python.exe in PATH enviroment
Are you in same directory than blah.py. Check this by issuing command -> edit blah.py and check if you can open this file
EDIT:
In that case you can not. (python arg means that you call python.exe whit some parameters which python assume that is filename of script you want to run)
You can create bat file whit lines in your path map and run .bat file
Example:
In one of Path maps create blah.py.bat
Edit file and put line
python C:\Somedir\blah.py
You can now run blah.py from anywere, becuase you do not need to put .bat extention when running bat files

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!

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.

How CMD.exe recognize an extension need program?

When I give the path of a .py file to cmd.exe , It run that file automatically using Python.(I added the path of python to PATH Environment Variable already).
I want know:
1- how cmd.exe recognize that my .py file must run with python?
2- If I want to remove .py from the end of my file name, And replace it with .wxyz (for example), How I can make cmd.exe behave with that file such as a .py file? (In the other word I mean I want to add .wxyz extension to the list of files that run with python)

Windows keeps a list of file extensions and the programs that should run them. You can see the current list and add your own by going to the control panel, searching for "Default Programs" and selecting the entry that says something like "Make a file type always open in a specific program" (it varies by windows version and language of course).
Alternately, you can do it on the command line with the assoc and ftype commands. I don't have a windows machine up at the moment, but type these and see what you get.
assoc .py
ftype File.Python
This will get you the help on how to change them
assoc /?
ftype /?

1) There is a good explanation here:
When the Shell needs to query for the file associations of a file type, it creates an array of registry keys containing the associations for the file type, and checks these keys for the appropriate file associations to use.
In short, when you installed Python, it equipped Windows with enough context to know it should call for Python when it sees .py
2) A concise explanation is found here, with more context here.
In Windows this can be accomplished by editing the registry, allowing Windows to recognize custom extensions.

Why don't I have to add 'python' before invoking Python script?

I am new to programming, and Python is my first language.
I've added Python to my Path, but when I use the Command Prompt, I don't have to add python before myscript.py as opposed to many tutorials I've seen. Here is an example:
C:\User\MyName>Welcome.py
Welcome to Python
Python is fun
When I enter 'python', there is a subsequent error:
C:\User\MyName>python Welcome.py
python: can't open file 'Welcome.py': [Errno 2] No such file or directory
Do I really need the 'python'?
Thanks in advance!

If you followed the Python on Windows FAQ, it seems that the standard Python installer has already taken the liberty of associating .py files with an open command to ..\..\Python\python.exe "%1" %*.
How do I make Python scripts executable?
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.
Who'd have thunk! This isn't the way it used to be four years ago when I first installed Python on my Windows machine.

Yes and no.
It really depends on how the script is written.
On most unix systems (Linux, Mac OS), you could include #!/bin/python to the top of (as the first line of) your script and therefore execute it by just calling the filename on the command line. That first line tells the shell that this file contains a python program. The shell then uses the python interpreter to execute the file (translation: it translates your $ Welcome.py to $ /bin/python Welcome.py <- note that python is being called explicitly and that it's the same path as what's on the first line of your file).
Presumably, the Windows OS can also be instructed in the same way, though I have never been able to do it myself, nor have I tried very hard (I moved away from windows about 5 years ago). This is why you'll need to explicitly call python.
Calling python tells the OS: "hey! open that program called python and tell it to run the file Welcome.py". This is exactly what the command /bin/python Welcome.py does on a unix system

When you install python on windows with a regular installer, .py files are associated with the python.exe you installed. When you type Welcome.py, Windows searches the local directory and then all paths in the PATH variable for a program called Welcome.py and runs it via python. Since this worked for you, it means that Welcome.py is somewhere on your path or in your local directory.
You can figure out your file associations with the assoc .py and ftype Python.File commands. The echo %PATH% and echo %PATHEXT% commands are also useful.
When you type python Welcome.py, Windows searches all paths in the PATH variable for a program that starts with 'python' and ends with an extension in PATHEXT. It finds 'python.exe' and runs it. Python in turn looks for a script called Welcome.py in the current directory. Since this didn't work for you, it means that Welcome.py is not in your local directory. It would have worked if you had given the right path to Welcome.py.
You can find out where Welcome.py is with the (not surprisingly) where Welcome.py command.
If you only have a single python installation, there is no need to call python myscript.py ....

How to write a script (for Windows XP) to run a python program?

Basically, I'd like to run a script (versus typing python program.py) or even have a shortcut that I could click on and start the program. Any ideas?

From python.org:
On Windows systems, there is no
notion of an “executable mode”. The
Python installer automatically
associates .py files with python.exe
so that a double-click on a Python
file will run it as a script. The
extension can also be .pyw, in that
case, the console window that normally
appears is suppressed.
Also from python.org:
On Windows 2000, 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.

Try using a batch file (.bat).
Type in whatever commands you want to execute in the proper order, in notepad, such as:
python program.py
Save the file as iHateTyping.bat
Open the command prompt using Run.
Go to the directory where you saved the file using cd.
Type in:
iHateTyping.bat
& you're done.
I encourage you to read more about batch files in the link highlighted above.

Press Ctrl+R, then type python.py to run your Python script.

Use py2exe to create a portable windows executable file.

How to execute Python scripts in Windows?

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?

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:
C:\>assoc .py
.py=Python.File
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:
C:\>ftype Python.File
Python.File="c:\python26\python.exe" "%1" %*
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:
"c:\python26\python.exe" "blah.py" foo
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
HKEY_CLASSES_ROOT\Applications\python26.exe\shell\open\command
key to:
"C:\Python26\python26.exe" "%1" %*
Likely, previously, %* was missing. Similarly, set
HKEY_CLASSES_ROOT\py_auto_file\shell\open\command
to the same value. See http://eli.thegreenplace.net/2010/12/14/problem-passing-arguments-to-python-scripts-on-windows/
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

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

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:\>

How to execute Python scripts in Windows?
You could install pylauncher. It is used to launch .py, .pyw, .pyc, .pyo files and supports multiple Python installations:
T\:> blah.py argument
You can run your Python script without specifying .py extension if you have .py, .pyw in PATHEXT environment variable:
T:\> blah argument
It adds support for shebang (#! header line) to select desired Python version on Windows if you have multiple versions installed. You could use *nix-compatible syntax #! /usr/bin/env python.
You can specify version explicitly e.g., to run using the latest installed Python 3 version:
T:\> py -3 blah.py argument
It should also fix your sys.argv issue as a side-effect.

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.

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.

Can you execute python.exe from any map?
If you do not, chek if you have proper values for python.exe in PATH enviroment
Are you in same directory than blah.py. Check this by issuing command -> edit blah.py and check if you can open this file
EDIT:
In that case you can not. (python arg means that you call python.exe whit some parameters which python assume that is filename of script you want to run)
You can create bat file whit lines in your path map and run .bat file
Example:
In one of Path maps create blah.py.bat
Edit file and put line
python C:\Somedir\blah.py
You can now run blah.py from anywere, becuase you do not need to put .bat extention when running bat files

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!

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.