How Should I Set Default Python Version In Windows

Question

I installed Python 2 6 and Python 3 1 on Windows 7 and set environment variable  path   d  python2 6  When I run python in cmd  it displays the python version 2 6  which is what I want   But  when I wrote a script in a bat file and ran it  the displayed python version was 3 1      import sys     print  sys version   What s going on here

User · Answer

Try modifying the path in the windows registry  HKEY LOCAL MACHINE SYSTEM CurrentControlSet Control Session Manager Environment    Caveat  Don t break the registry

User · Answer

If you are a Windows user and you have a version of Python 3 3 or greater  you should have the Python Launcher for Windows installed on your machine  which is the recommended way to use for launching all python scripts  regardless of python version the script requires   As a user  Always type py instead of python when running a script from the command line   Setup your  quot Open with    quot  explorer default program association with C  Windows py exe  Set the command line file extension association to use the Python Launcher for Windows  this will make typing py optional   ftype Python File  quot C  windows py exe quot   quot  L quot     ftype Python NoConFile  quot C  Windows pyw exe quot   quot  L quot      Set your preferred default version by setting the PY PYTHON environment variable  e g  PY PYTHON 3 7    You can see what version of python is your default by typing py   You can also set PY PYTHON3 or PY PYTHON2 to specify default python 3 and python 2 versions  if you have multiple    If you need to run a specific version of python  you can use py -M m  where M is the major version and m is the minor version    For example  py -3 will run any installed version of python 3   List the installed versions of python with py -0    As a script writer  Include a shebang line at the top of your script that indicates the major version number of python required   If the script is not compatible with any other minor version   include the minor version number as well   For example     usr bin env python3  You can use the shebang line to indicate a virtual environment as well  see PEP 486 below      See also  PEP 397 -- Python launcher for Windows PEP 486 -- Make the Python Launcher aware of virtual environments Python Launcher for Windows - User Guide

User · Answer

This worked for me   Go to  Control Panel System and Security System   select  Advanced system settings from the left panel from Advanced tab click on Environment Variables   In the System variables section search for  create if doesn t exist   PYTHONPATH   and set  C  Python27  C  Python27 Scripts    or your desired version  You need to restart CMD   In case it still doesn t work you might want to leave in the PATH variable only your desired version

User · Answer

This work for me   If you want to use the python 3 6 you must move the python3 6 on the top of the list   The same applies to the python2 7 If you want to have the 2 7 as default then make sure you move the python2 7 on the very top on the list      step 1        step 2        step 3     then close any cmd command prompt and opened again  it should work as expected      python --version    gt  gt  gt  Python 3 6

User · Answer

Check which one the system is currently using   python --version   Add the main folder location  e g  C ProgramFiles  and Scripts location  C ProgramFiles Scripts  to Environment Variables of the system  Add both 3 x version and 2 x version  Path location is ranked inside environment variable  If you want to use Python 2 x simply put path of python 2 x first  if you want for Python 3 x simply put 3 x first  This uses python 2

User · Answer

Now that Python 3 3 is released it is easiest to use the py exe utility described here  http   www python org dev peps pep-0397   It allows you to specify a Python version in your script file using a UNIX style directive   There are also command line and environment variable options for controlling which version of Python is run   The easiest way to get this utility is to install Python 3 3 or later

User · Answer

Running  py  command will tell you what version you have running  If you currently running 3 x and you need to switch to 2 x  you will need to use switch  -2   py -2   If you need to switch from python 2 x to python 3 x you will have to use  -3  switch  py -3   If you would like to have Python 3 x as a default version  then you will need to create environment variable  PY PYTHON  and set it s value to 3

User · Answer

See here for original post      This is an example of how a Python Launcher  ini file is structured    If you want to use it  copy it to py ini and make your changes there    after removing this header comment    This file will be removed on launcher uninstallation and overwritten   when the launcher is installed or upgraded  so don t edit this file   as your changes will be lost     defaults    Uncomment out the following line to have Python 3 be the default   python 3   commands    Put in any customised commands you want here  in the format   that s shown in the example line  You only need quotes around the   executable if the path has spaces in it      You can then use e g    myprog as your shebang line in scripts  and   the launcher would invoke e g       c  Program Files MyCustom exe  -a -b -c myscript py    myprog  c  Program Files MyCustom exe  -a -b -c   Thus  on my system I made a py ini file under c  windows  where py exe exists  with the following contents    defaults  python 3   Now when you Double-click on a  py file  it will be run by the new default version  Now I m only using the Shebang    python2 on my old scripts

User · Answer

The Python installer installs Python Launcher for Windows   This program  py exe  is associated with the Python file extensions and looks for a  quot shebang quot  comment to specify the python version to run   This allows many versions of Python to co-exist and allows Python scripts to explicitly specify which version to use  if desired   If it is not specified  the default is to use the latest Python version for the current architecture  x86 or x64    This default can be customized through a py ini file or PY PYTHON environment variable   See the docs for more details  Newer versions of Python update the launcher   The latest version has a py -0 option to list the installed Pythons and indicate the current default  Here s how to check if the launcher is registered correctly from the console  C   gt assoc  py  py Python File  C   gt ftype Python File Python File  quot C  Windows py exe quot   quot  1 quot      Above   py files are associated with the Python File type   The command line for Python File is the Python Launcher  which is installed in the Windows directory since it is always in the PATH  For the association to work  run scripts from the command line with script py  not  quot python script py quot   otherwise python will be run instead of py   If fact it s best to remove Python directories from the PATH  so  quot python quot  won t run anything and enforce using py  py exe can also be run with switches to force a Python version  py -3 script py         select latest Python 3 X version to be used  py -3 6 script py       select version 3 6 specifically  py -3 9-32 script py    select version 3 9 32-bit specifically  py -0                   list installed Python versions  latest PyLauncher    Additionally  add  py  pyw  pyc  pyo to the PATHEXT environment variable and then the command line can just be script with no extension

User · Answer

Edit registry key HKEY LOCAL MACHINE SOFTWARE Microsoft Windows CurrentVersion App Paths python exe default Set default program to open  py files to python exe

User · Answer

If you know about Environment variables and the system variable called path  consider that any version of any binary which comes sooner  will be used as default   Look at the image below  I have 3 different python versions but python 3 8 will be used as default since it came sooner than the other two   In case of mentioned image  sooner means higher

User · Answer

This is if you have both the versions installed    Go to This PC - gt  Right-click - gt  Click on Properties - gt  Advanced System Settings   You will see the System Properties  From here navigate to the  Advanced  Tab -  Click on Environment Variables   You will see a top half for the user variables and the bottom half for System variables    Check the System Variables and double-click on the Path to edit the Path    Check for the path of Python which you wish to run i e  Python 2 x or 3 x  and move it to the top of the Path list    Restart the Command Prompt  and now when you check the version of Python  it should correctly display the required version

User · Answer

Nothing above worked  this is what worked for me    ftype Python File C  Path to python exe   1       This command should be run in Command prompt launched as administrator  Warning  even if the path in this command is set to python35   if you have python36 installed it s going to set the default to python36  To prevent this  you can temporarily change the folder name from Python36 to xxPython36  run the command and then remove the change to the Python 36 folder

User · Answer

Use SET command in Windows CMD to temporarily set the default python for the current session   SET PATH C  Program Files Python 3 5

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