py launcher does not find my Python 2.7

Question

I'm on Windows 7. I have Python 2.7 installed for years. I installed recently Python 3.4. I'm trying to use the new py launcher. When I open the cmd terminal and type py -2, I get this error message: Requested Python version (2) not installed. How can make py aware of my python 2.7 installation?

Note: python 2.7 is installed in a non-standard directory (not in C:\Python27), in case this is the problem.

I tried installing 2.7.8 in a nonstandard directory (literally C:\Python_non_standard_directory) and made sure the Add python.exe to Path option was unchecked. The result of that install was that py -2 still worked as expected, as did py -3. Unfortunately, I don't have any recommendations, but I thought that my test might help put you on the right track. — Matthew Champion
– Matthew Champion, Commented Dec 16, 2014 at 11:07
Just to clarify: did you install python 2.7.8 after installing python 3? — Dan737
– Dan737, Commented Dec 16, 2014 at 15:21
I had Python 3.4.1 installed to begin with before installing 2.7.8. — Matthew Champion
– Matthew Champion, Commented Dec 16, 2014 at 15:27
if python3 was installed first then just uninstall the pylauncher and modify python3 in controlpanel — Smart Manoj
– Smart Manoj, Commented Jul 9, 2017 at 9:31

Dan737 · Accepted Answer · 2014-12-17 10:31:20Z

9

I found the solution. The registry had wrong entries. As I have a 32 bit version installed I went to HKEY_LOCAL_MACHINE|HKEY_CURRENT_USER\SOFTWARE\wow6432node\Python\PythonCore\2.7\InstallPath and the value was set to C:\Python27 while my installation is in D:\Python27. So I changed all the registry values to match the correct location and it now works fine.

It's been quite a while I installed Python 2.7, but I assume I had Python 2.7 installed first. Then I deleted it and installed pythonxy in this new location. I probably didn't uninstall the previous version correctly.

answered Dec 17, 2014 at 10:31

Dan737

4514 gold badges7 silver badges27 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

poleguy Over a year ago

This also works to get py.exe to run an anaconda version of python. Just add the appropriate key and point it to the anaconda path.

TT-- Over a year ago

There are actually three locations in the registry, and the py launcher picks from HKCU according to python.org/dev/peps/pep-0514/#structure

Marcello B. · Accepted Answer · 2018-10-09 23:47:34Z

5

I had a similar issue with Py Launcher failing to recognize my Python 2.7 install. I found editing the Windows Registry (Windows 10) by adding 2.7 to [HKEY_CURRENT_USER\Software\Python\PythonCore\2.7] solved my problem.

Other Window versions may have the PythonCore key in a different location.

Here is the full export of the tree I added:

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\Python\PythonCore\2.7]

[HKEY_CURRENT_USER\Software\Python\PythonCore\2.7\InstallPath]
"ExecutablePath"="C:\\Users\\kcec11\\Python\\Python27\\python.exe"
"WindowedExecutablePath"="C:\\Users\\kcec11\\Python\\Python27\\pythonw.exe"
@="C:\\Users\\kcec11\\Python\\Python27\\"

edited Oct 9, 2018 at 23:47

Marcello B.

4,47011 gold badges48 silver badges72 bronze badges

answered Oct 9, 2018 at 20:46

Carl C

511 silver badge2 bronze badges

Comments

Community · Accepted Answer · 2017-05-23 12:10:04Z

0

Usually, this kind of problem in Windows occurs because Python isn't in the OS path defined as an environment variable.

As in this question, try going to the "Advanced System Settings", edit "Environment Variables" and include ;C:\python27 (in your case, the place where you installed Python 2.7) to the path.

edited May 23, 2017 at 12:10

CommunityBot

11 silver badge

answered Dec 16, 2014 at 11:06

Matheus Portela

2,4701 gold badge23 silver badges32 bronze badges

1 Comment

Dan737 Over a year ago

My python path is D:\Python27. If I run from the terminal echo %PATH% I can find D:\Python27. Also I can run python 2 from the terminal by typing python.

DisappointedByUnaccountableMod · Accepted Answer · 2021-02-02 17:50:02Z

Old question, another answer - trying out my codebase which I've been using with 3.8.3 for quite a while and I was wanting to test with 3.9.1 because I've experienced getting too far behind the version number curve before to want to experience it again, so using a clean env with just 3.9.1 installed, trying to run from source it gave this error:

Requested Python version (3.8) is not installed

After fifteen minutes of head scratching and searching without any result, and I already can't remember why I checked this but it turns out I had a shebang in line 1 of my main .py file (I'm on Windows):

#!/usr/local/bin/python3.8

change this to:

#!/usr/local/bin/python3.9

and now it works with Python 3.9.1 :-)

See https://docs.python.org/3/using/windows.html

Collectives™ on Stack Overflow

py launcher does not find my Python 2.7

4 Answers 4

2 Comments

Comments

1 Comment

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

2 Comments

Comments

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related