Can I install Python 3 x and 2 x on the same Windows computer

Question

I m running Windows and the shell OS automatically runs Python based on the registry settings when you run a program on the command line  Will this break if I install a 2 x and 3 x version of Python on the same machine   I want to play with Python 3 while still being able to run 2 x scripts on the same machine

User · Answer

I m using 2 5  2 6  and 3 0 from the shell with one line batch scripts of the form      The   symbol at the start turns off the prompt from displaying the command     The   represents an argument  while the   means all of them   c  programs pythonX Y python exe      Name them pythonX Y bat and put them somewhere in your PATH  Copy the file for the preferred minor version  i e  the latest  to pythonX bat   E g  copy python2 6 bat python2 bat   Then you can use python2 file py from anywhere   However  this doesn t help or even affect the Windows file association situation  For that you ll need a launcher program that reads the    line  and then associate that with  py and  pyw files

User · Answer

The official solution for coexistence seems to be the Python Launcher for Windows  PEP 397 which was included in Python 3 3 0   Installing the release dumps py exe and pyw exe launchers into  SYSTEMROOT   C  Windows  which is then associated with py and pyw scripts  respectively   In order to use the new launcher  without manually setting up your own associations to it   leave the  Register Extensions  option enabled   I m not quite sure why  but on my machine it left Py 2 7 as the  default   of the launcher    Running scripts by calling them directly from the command line will route them through the launcher and parse the shebang  if it exists    You can also explicitly call the launcher and use switches  py -3 mypy2script py     All manner of shebangs seem to work     C  Python33 python exe   python3    usr bin env python3   as well as wanton abuses      notepad exe

User · Answer

Before I courageously installed both simultaneously  I had so many questions  If I give python will it go to py3 when i want py2  pip virtualenv will happen under py2 3   It seems to be very simple now   Just blindly install both of them  Make sure you get the right type x64 x32   While after installing make sure you add to the path to your environment variables    ENVIRONMENT   SETENVIRONMENTVARIABLE  PATH     ENV PATH C  PYTHONx    USER     Replace the x in the command above to set the path   Then go to both the folders    Navigate to  python3 6 Scripts    and rename pip to pip3   If pip3 already exists delete the pip  This will make sure that just pip will run under python2  You can verify by   pip --version   In case you want to use pip with python3 then just use   pip3 install    You can similarly do the same to python file and others   Cheers

User · Answer

Here you go     winpylaunch py      Looks for a directive in the form     C  Python30 python exe   The directive must start with    and contain   exe     This will be assumed to be the correct python interpreter to   use to run the script ON WINDOWS  If no interpreter is   found then the script will be run with  python exe     ie  whatever one is found on the path    For example  in a script which is saved as utf-8 and which   runs on Linux and Windows and uses the Python 2 6 interpreter              usr bin python        C  Python26 python exe        - - coding  utf-8 - -     When run on Linux  Linux uses the  usr bin python  When run   on Windows using winpylaunch py it uses C  Python26 python exe      To set up the association add this to the registry           HKEY CLASSES ROOT Python File shell open command       Default  REG SZ    C  Python30 python exe  S  usr bin winpylaunch py   1         NOTE  winpylaunch py itself works with either 2 6 and 3 0  Once   this entry has been added python files can be run on the   commandline and the use of winpylaunch py will be transparent     import subprocess import sys  USAGE       USAGE  winpylaunch py  lt script py gt   arg1   arg2          if   name         main       if len sys argv   gt  1      script   sys argv 1      args     sys argv 2       if script endswith   py          interpreter    python exe    Default to wherever it is found on the path        lines   open script  readlines         for line in lines          if line startswith       and line find   exe      -1            interpreter   line 2   strip             break       process   subprocess Popen  interpreter     script    args        process wait         sys exit     print USAGE    I ve just knocked this up on reading this thread  because it s what I was needing too   I have Pythons 2 6 1 and 3 0 1 on both Ubuntu and Windows  If it doesn t work for you post fixes here

User · Answer

You should make sure that the PATH environment variable doesn t contain both python exe files   add the one you re currently using to run scripts on a day to day basis     or do as Kniht suggested with the batch files   Aside from that   I don t see why not    P S   I have 2 6 installed as my  primary  python and 3 0 as my  play  python   The 2 6 is included in the PATH   Everything works fine

User · Answer

The Python installation normally associates  py   pyw and  pyc files with the Python interpreter  So you can run a Python script either by double-clicking it in Explorer or by typing its name in a command-line window  so no need to type python scriptname py  just scriptname py will do    If you want to manually change this association  you can edit these keys in the Windows registry   HKEY CLASSES ROOT Python File shell open command HKEY CLASSES ROOT Python NoConFile shell open command HKEY CLASSES ROOT Python CompiledFile shell open command   Python Launcher  People have been working on a Python launcher for Windows  a lightweight program associated with  py and  pyw files which would look for a  shebang  line  similar to Linux et al  on the first line  and launch Python 2 x or 3 x as required  See  A Python Launcher for Windows  blog post for details

User · Answer

As far as I know Python runs off of the commandline using the PATH variable as opposed to a registry setting   So if you point to the correct version on your PATH you will use that  Remember to restart your command prompt to use the new PATH settings

User · Answer

Try using Anaconda  Using the concept of Anaconda environments  let   s say you need Python 3 to learn programming  but you don   t want to wipe out your Python 2 7 environment by updating Python  You can create and activate a new environment named  quot snakes quot   or whatever you want   and install the latest version of Python 3 as follows  conda create --name snakes python 3  Its simpler than it sounds  take a look at the intro page here  Getting Started with Anaconda And then to handle your specific problem of having version 2 x and 3 x running side by side  see   Managing Python Versions with Anaconda Switching between Python 2 and Python 3 environments

User · Answer

I m using 2 5  2 6  and 3 0 from the shell with one line batch scripts of the form      The   symbol at the start turns off the prompt from displaying the command     The   represents an argument  while the   means all of them   c  programs pythonX Y python exe      Name them pythonX Y bat and put them somewhere in your PATH  Copy the file for the preferred minor version  i e  the latest  to pythonX bat   E g  copy python2 6 bat python2 bat   Then you can use python2 file py from anywhere   However  this doesn t help or even affect the Windows file association situation  For that you ll need a launcher program that reads the    line  and then associate that with  py and  pyw files

User · Answer

I m using 2 5  2 6  and 3 0 from the shell with one line batch scripts of the form      The   symbol at the start turns off the prompt from displaying the command     The   represents an argument  while the   means all of them   c  programs pythonX Y python exe      Name them pythonX Y bat and put them somewhere in your PATH  Copy the file for the preferred minor version  i e  the latest  to pythonX bat   E g  copy python2 6 bat python2 bat   Then you can use python2 file py from anywhere   However  this doesn t help or even affect the Windows file association situation  For that you ll need a launcher program that reads the    line  and then associate that with  py and  pyw files

User · Answer

I am just starting out with python now  I m reading Zed Shaw s book  Learn Python the Hard Way  which requires python version 2 x but am also taking a class that requires python 3 x  So here is what I did     Download python 2 7 run power shell  should already be installed on windows  run python IN POWERSHELL  if it doesn t recognize then go to step 4  Only if powershell doesn t recognize python 2 7 type in the following       ENVIRONMENT   SETENVIRONMENTVARIABLE  PATH     ENV PATH C  PYTHON27    USER     no outside quotes    Now type python and you should see it say python 2 7 blah blah blah   NOW for python 3 x  Simple  python 3 x download comes with python for windows app  SO simply pin the Python for Windows app to your task bar  or create shortcut to the desktop and you are done   Open Python for Windows for 3 x  Open Powershell for python 2 x  I hope this helps

User · Answer

Easy-peasy  after installing both the python versions add the paths to the environment variables  see  Then go to python 2 and python 3 folders and rename them to python2 and python3 respectively as shown  and   Now in cmd type python2 or python3 to use your required version see

User · Answer

I would assume so  I have Python 2 4  2 5 and 2 6 installed side-by-side on the same computer

User · Answer

As far as I know Python runs off of the commandline using the PATH variable as opposed to a registry setting   So if you point to the correct version on your PATH you will use that  Remember to restart your command prompt to use the new PATH settings

User · Answer

Here is a neat and clean way to install Python2  amp  Python3 on windows   https   datascience com co how-to-install-python-2-7-and-3-6-in-windows-10-add-python-path-281e7eae62a  My case  I had to install Apache cassandra  I already had Python3 installed in my D  drive  With loads of development work under process i didn t wanted to mess my Python3 installation  And  i needed Python2 only for Apache cassandra    So i took following steps    Downloaded  amp  Installed Python2  Added Python2 entries to classpath  C  Python27 C  Python27 Scripts  Modified python exe to python2 exe  as shown in image below       Now i am able to run both  For Python 2 python2 --version   amp  Python 3  python --version       So  my Python3 installation remained intact

User · Answer

When you add both to environment variables there will a be a conflict because the two executable have the same name  python exe   Just rename one of them  In my case I renamed it to python3 exe   So when I run python it will execute python exe which is 2 7    and when I run python3 it will execute python3 exe which is 3 6

User · Answer

As far as I know Python runs off of the commandline using the PATH variable as opposed to a registry setting   So if you point to the correct version on your PATH you will use that  Remember to restart your command prompt to use the new PATH settings

User · Answer

You should make sure that the PATH environment variable doesn t contain both python exe files   add the one you re currently using to run scripts on a day to day basis     or do as Kniht suggested with the batch files   Aside from that   I don t see why not    P S   I have 2 6 installed as my  primary  python and 3 0 as my  play  python   The 2 6 is included in the PATH   Everything works fine

User · Answer

You should make sure that the PATH environment variable doesn t contain both python exe files   add the one you re currently using to run scripts on a day to day basis     or do as Kniht suggested with the batch files   Aside from that   I don t see why not    P S   I have 2 6 installed as my  primary  python and 3 0 as my  play  python   The 2 6 is included in the PATH   Everything works fine

User · Answer

I would assume so  I have Python 2 4  2 5 and 2 6 installed side-by-side on the same computer

User · Answer

Here s my setup    Install both Python 2 7 and 3 4 with the windows installers  Go to C  Python34  the default install path  and change python exe to python3 exe Edit your environment variables to include C  Python27  C  Python27 Scripts  C  Python34  C  Python34 Scripts     Now in command line you can use python for 2 7 and python3 for 3 4

User · Answer

I m using 2 5  2 6  and 3 0 from the shell with one line batch scripts of the form      The   symbol at the start turns off the prompt from displaying the command     The   represents an argument  while the   means all of them   c  programs pythonX Y python exe      Name them pythonX Y bat and put them somewhere in your PATH  Copy the file for the preferred minor version  i e  the latest  to pythonX bat   E g  copy python2 6 bat python2 bat   Then you can use python2 file py from anywhere   However  this doesn t help or even affect the Windows file association situation  For that you ll need a launcher program that reads the    line  and then associate that with  py and  pyw files

User · Answer

Here is how to run Python 2 and 3 on the same machine     install Python 2 x    install Python 3 x   Start Powershell    Type Python -2 to launch Python 2 x  Type Python -3 to launch Python 2 x    The Python Launcher for Windows was embedded into Python since Version 3 3  as promised in 2011 when the Stand alone first made its debut   Python Launcher for Windows

User · Answer

I had the same problem where I wanted to use python3 for most work but IDA pro required python2  SO  here s what I did   I first created 3 variables in the user environment variable as follows    PYTHON ACTIVE   This is initially empty HOME PYTHON27   Has a path to a folder where Python 2 is installed  Eg     scripts   HOME PYTHON38   Similar to python 2  this variable contains a path to python 3 folders    Now I added       PYTHON ACTIVE    to PATH variable  So  basically saying that whatever this  PYTHON ACTIVE  contains is the active python  We programmatically change the contains of  PYTHON ACTIVE  to switch python version   Here is the example script      This batch file is used to switch between python 2 and 3   ECHO OFF  set  p choice   Please enter  27  for python 2 7    38  for python 3 8      IF  choice   27   setx PYTHON ACTIVE  HOME PYTHON27     IF  choice   38   setx PYTHON ACTIVE  HOME PYTHON38      PAUSE   This script takes python version as input and accordingly copies HOME PYTHON27 or HOME PYTHON38 to PYTHON ACTIVE  Thus changing the global Python version

User · Answer

From version 3 3 Python introduced Launcher for Windows utility https   docs python org 3 using windows html python-launcher-for-windows   So to be able to use multiple versions of Python    install Python 2 x  x is any version you need  install Python 3 x  x is any version you need also you have to have one version 3 x    3 3   open Command Prompt  type py -2 x to launch Python 2 x type py -3 x to launch Python 3 x

User · Answer

I would assume so  I have Python 2 4  2 5 and 2 6 installed side-by-side on the same computer

User · Answer

I am just starting out with python now  I m reading Zed Shaw s book  Learn Python the Hard Way  which requires python version 2 x but am also taking a class that requires python 3 x  So here is what I did     Download python 2 7 run power shell  should already be installed on windows  run python IN POWERSHELL  if it doesn t recognize then go to step 4  Only if powershell doesn t recognize python 2 7 type in the following       ENVIRONMENT   SETENVIRONMENTVARIABLE  PATH     ENV PATH C  PYTHON27    USER     no outside quotes    Now type python and you should see it say python 2 7 blah blah blah   NOW for python 3 x  Simple  python 3 x download comes with python for windows app  SO simply pin the Python for Windows app to your task bar  or create shortcut to the desktop and you are done   Open Python for Windows for 3 x  Open Powershell for python 2 x  I hope this helps

User · Answer

The Python installation normally associates  py   pyw and  pyc files with the Python interpreter  So you can run a Python script either by double-clicking it in Explorer or by typing its name in a command-line window  so no need to type python scriptname py  just scriptname py will do    If you want to manually change this association  you can edit these keys in the Windows registry   HKEY CLASSES ROOT Python File shell open command HKEY CLASSES ROOT Python NoConFile shell open command HKEY CLASSES ROOT Python CompiledFile shell open command   Python Launcher  People have been working on a Python launcher for Windows  a lightweight program associated with  py and  pyw files which would look for a  shebang  line  similar to Linux et al  on the first line  and launch Python 2 x or 3 x as required  See  A Python Launcher for Windows  blog post for details

User · Answer

Here is a neat and clean way to install Python2  amp  Python3 on windows   https   datascience com co how-to-install-python-2-7-and-3-6-in-windows-10-add-python-path-281e7eae62a  My case  I had to install Apache cassandra  I already had Python3 installed in my D  drive  With loads of development work under process i didn t wanted to mess my Python3 installation  And  i needed Python2 only for Apache cassandra    So i took following steps    Downloaded  amp  Installed Python2  Added Python2 entries to classpath  C  Python27 C  Python27 Scripts  Modified python exe to python2 exe  as shown in image below       Now i am able to run both  For Python 2 python2 --version   amp  Python 3  python --version       So  my Python3 installation remained intact

User · Answer

From version 3 3 Python introduced Launcher for Windows utility https   docs python org 3 using windows html python-launcher-for-windows   So to be able to use multiple versions of Python    install Python 2 x  x is any version you need  install Python 3 x  x is any version you need also you have to have one version 3 x    3 3   open Command Prompt  type py -2 x to launch Python 2 x type py -3 x to launch Python 3 x

User · Answer

Try using Anaconda  Using the concept of Anaconda environments  let   s say you need Python 3 to learn programming  but you don   t want to wipe out your Python 2 7 environment by updating Python  You can create and activate a new environment named  quot snakes quot   or whatever you want   and install the latest version of Python 3 as follows  conda create --name snakes python 3  Its simpler than it sounds  take a look at the intro page here  Getting Started with Anaconda And then to handle your specific problem of having version 2 x and 3 x running side by side  see   Managing Python Versions with Anaconda Switching between Python 2 and Python 3 environments

User · Answer

I had the same problem where I wanted to use python3 for most work but IDA pro required python2  SO  here s what I did   I first created 3 variables in the user environment variable as follows    PYTHON ACTIVE   This is initially empty HOME PYTHON27   Has a path to a folder where Python 2 is installed  Eg     scripts   HOME PYTHON38   Similar to python 2  this variable contains a path to python 3 folders    Now I added       PYTHON ACTIVE    to PATH variable  So  basically saying that whatever this  PYTHON ACTIVE  contains is the active python  We programmatically change the contains of  PYTHON ACTIVE  to switch python version   Here is the example script      This batch file is used to switch between python 2 and 3   ECHO OFF  set  p choice   Please enter  27  for python 2 7    38  for python 3 8      IF  choice   27   setx PYTHON ACTIVE  HOME PYTHON27     IF  choice   38   setx PYTHON ACTIVE  HOME PYTHON38      PAUSE   This script takes python version as input and accordingly copies HOME PYTHON27 or HOME PYTHON38 to PYTHON ACTIVE  Thus changing the global Python version

User · Answer

Easy-peasy  after installing both the python versions add the paths to the environment variables  see  Then go to python 2 and python 3 folders and rename them to python2 and python3 respectively as shown  and   Now in cmd type python2 or python3 to use your required version see

User · Answer

I think there is an option to setup the windows file association for  py files in the installer   Uncheck it and you should be fine   If not  you can easily re-associate  py files with the previous version   The simplest way is to right click on a  py file  select  open with     choose program    On the dialog that appears  select or browse to the version of python you want to use by default  and check the  always use this program to open this kind of file  checkbox

User · Answer

You can have both installed   You should write this in front of your script      bin env python2 7   or  eventually        bin env python3 6   Update  My solution works perfectly with Unix  after a quick search on Google  here is the Windows solution     c  Python python3 6 exe -u   Same thing  in front of your script

User · Answer

Before I courageously installed both simultaneously  I had so many questions  If I give python will it go to py3 when i want py2  pip virtualenv will happen under py2 3   It seems to be very simple now   Just blindly install both of them  Make sure you get the right type x64 x32   While after installing make sure you add to the path to your environment variables    ENVIRONMENT   SETENVIRONMENTVARIABLE  PATH     ENV PATH C  PYTHONx    USER     Replace the x in the command above to set the path   Then go to both the folders    Navigate to  python3 6 Scripts    and rename pip to pip3   If pip3 already exists delete the pip  This will make sure that just pip will run under python2  You can verify by   pip --version   In case you want to use pip with python3 then just use   pip3 install    You can similarly do the same to python file and others   Cheers

User · Answer

Hmm  I did this right now by just downloading Python 3 6 5 for Windows at https   www python org downloads release python-365  and made sure that the launcher would be installed  Then  I followed the instructions for using python 2 and python 3  Restart the command prompt and then use py -2 7 to use Python 2 and py or py -3 6 to use Python 3  You can also use pip2 for Python 2 s pip and pip for Python 3 s pip

User · Answer

Here s my setup    Install both Python 2 7 and 3 4 with the windows installers  Go to C  Python34  the default install path  and change python exe to python3 exe Edit your environment variables to include C  Python27  C  Python27 Scripts  C  Python34  C  Python34 Scripts     Now in command line you can use python for 2 7 and python3 for 3 4

User · Answer

You can have both installed   You should write this in front of your script      bin env python2 7   or  eventually        bin env python3 6   Update  My solution works perfectly with Unix  after a quick search on Google  here is the Windows solution     c  Python python3 6 exe -u   Same thing  in front of your script

User · Answer

Hmm  I did this right now by just downloading Python 3 6 5 for Windows at https   www python org downloads release python-365  and made sure that the launcher would be installed  Then  I followed the instructions for using python 2 and python 3  Restart the command prompt and then use py -2 7 to use Python 2 and py or py -3 6 to use Python 3  You can also use pip2 for Python 2 s pip and pip for Python 3 s pip

User · Answer

Here is how to run Python 2 and 3 on the same machine     install Python 2 x    install Python 3 x   Start Powershell    Type Python -2 to launch Python 2 x  Type Python -3 to launch Python 2 x    The Python Launcher for Windows was embedded into Python since Version 3 3  as promised in 2011 when the Stand alone first made its debut   Python Launcher for Windows

User · Answer

I think there is an option to setup the windows file association for  py files in the installer   Uncheck it and you should be fine   If not  you can easily re-associate  py files with the previous version   The simplest way is to right click on a  py file  select  open with     choose program    On the dialog that appears  select or browse to the version of python you want to use by default  and check the  always use this program to open this kind of file  checkbox

User · Answer

When you add both to environment variables there will a be a conflict because the two executable have the same name  python exe   Just rename one of them  In my case I renamed it to python3 exe   So when I run python it will execute python exe which is 2 7    and when I run python3 it will execute python3 exe which is 3 6

User · Answer

I would assume so  I have Python 2 4  2 5 and 2 6 installed side-by-side on the same computer

User · Answer

Here you go     winpylaunch py      Looks for a directive in the form     C  Python30 python exe   The directive must start with    and contain   exe     This will be assumed to be the correct python interpreter to   use to run the script ON WINDOWS  If no interpreter is   found then the script will be run with  python exe     ie  whatever one is found on the path    For example  in a script which is saved as utf-8 and which   runs on Linux and Windows and uses the Python 2 6 interpreter              usr bin python        C  Python26 python exe        - - coding  utf-8 - -     When run on Linux  Linux uses the  usr bin python  When run   on Windows using winpylaunch py it uses C  Python26 python exe      To set up the association add this to the registry           HKEY CLASSES ROOT Python File shell open command       Default  REG SZ    C  Python30 python exe  S  usr bin winpylaunch py   1         NOTE  winpylaunch py itself works with either 2 6 and 3 0  Once   this entry has been added python files can be run on the   commandline and the use of winpylaunch py will be transparent     import subprocess import sys  USAGE       USAGE  winpylaunch py  lt script py gt   arg1   arg2          if   name         main       if len sys argv   gt  1      script   sys argv 1      args     sys argv 2       if script endswith   py          interpreter    python exe    Default to wherever it is found on the path        lines   open script  readlines         for line in lines          if line startswith       and line find   exe      -1            interpreter   line 2   strip             break       process   subprocess Popen  interpreter     script    args        process wait         sys exit     print USAGE    I ve just knocked this up on reading this thread  because it s what I was needing too   I have Pythons 2 6 1 and 3 0 1 on both Ubuntu and Windows  If it doesn t work for you post fixes here

User · Answer

The official solution for coexistence seems to be the Python Launcher for Windows  PEP 397 which was included in Python 3 3 0   Installing the release dumps py exe and pyw exe launchers into  SYSTEMROOT   C  Windows  which is then associated with py and pyw scripts  respectively   In order to use the new launcher  without manually setting up your own associations to it   leave the  Register Extensions  option enabled   I m not quite sure why  but on my machine it left Py 2 7 as the  default   of the launcher    Running scripts by calling them directly from the command line will route them through the launcher and parse the shebang  if it exists    You can also explicitly call the launcher and use switches  py -3 mypy2script py     All manner of shebangs seem to work     C  Python33 python exe   python3    usr bin env python3   as well as wanton abuses      notepad exe

User · Answer

I think there is an option to setup the windows file association for  py files in the installer   Uncheck it and you should be fine   If not  you can easily re-associate  py files with the previous version   The simplest way is to right click on a  py file  select  open with     choose program    On the dialog that appears  select or browse to the version of python you want to use by default  and check the  always use this program to open this kind of file  checkbox

User · Answer

You can have both installed   You should write this in front of your script      bin env python2 7   or  eventually        bin env python3 6   Update  My solution works perfectly with Unix  after a quick search on Google  here is the Windows solution     c  Python python3 6 exe -u   Same thing  in front of your script

User · Answer

I think there is an option to setup the windows file association for  py files in the installer   Uncheck it and you should be fine   If not  you can easily re-associate  py files with the previous version   The simplest way is to right click on a  py file  select  open with     choose program    On the dialog that appears  select or browse to the version of python you want to use by default  and check the  always use this program to open this kind of file  checkbox

User · Answer

As far as I know Python runs off of the commandline using the PATH variable as opposed to a registry setting   So if you point to the correct version on your PATH you will use that  Remember to restart your command prompt to use the new PATH settings

User · Answer

You can have both installed   You should write this in front of your script      bin env python2 7   or  eventually        bin env python3 6   Update  My solution works perfectly with Unix  after a quick search on Google  here is the Windows solution     c  Python python3 6 exe -u   Same thing  in front of your script

User · Answer

You should make sure that the PATH environment variable doesn t contain both python exe files   add the one you re currently using to run scripts on a day to day basis     or do as Kniht suggested with the batch files   Aside from that   I don t see why not    P S   I have 2 6 installed as my  primary  python and 3 0 as my  play  python   The 2 6 is included in the PATH   Everything works fine

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