ROOT 6 and Python 3 on Windows 10: How well does it work?

ROOT Version: 6.22/02, 6.24/02
Platform: Windows 10 (1809 upgraded to 20H2)
Compiler: Visual Studio 2019 (v16.6.5)

Dear ROOT developers,

ROOT 6.24 seems to support Python 3 on Windows 10 as it is shown in ROOT installation and PyROOT on Windows 10.

Thank you for your efforts. We are eager to test it and compare the results with

I have several questions about how well PyROOT works on Windows.

Nightlies and CI

Your page

mentions another to access Jenkins instance: However, I wasn’t able
to login with my account created by my client (CEA):

Access denied.

You are not authorized to access this site: with these credentials or this authentication system.

Can you tell me how to access to your jobs details?
I would like to know which tests pass on Windows.

Tests with PyROOT 6.22

Some tests were carried out with ROOT 6.22/02 and Python 2.7 (Miniconda). Here
is a summary :

  • creating a TCanvas failed with Python but succeeded with IPython.
  • callback doesn’t seem to work using ROOT.gROOT.LoadMacro().
  • creating a cppyy.gbl.std.vector[int]() failed.

And an issue with NumPy requires further investigation ('numpy.ndarray' object has no attribute 'typecode' [...]).

Do you know if those problems are solved with ROOT 6.24?

Relationship with Visual Studio 2019

You don’t seem to recommend a precise version of Visual Studio 2019 like in
Windows ROOT problem. Does it mean that
ROOT 6.24 doesn’t care about the version of VS 2019 to be

And is it mandatory to use the Developer Prompt? In most cases, cmd.exe seems to

Best regards,


I think you need a CERN account (maybe @Axel can give more details)

The nightly build gives 100% tests passed, 0 tests failed out of 1790. Do you want the complete (unordered) list?

For the python issues, I’m not sure if they are Windows dependent. I hope @etejedor can give you more details (or come back to me if they are only Windows related issues)

EDIT: What I can tell is that the GUI isn’t working properly on Windows (the events are not processed by the main event loop)

And about the Relationship with Visual Studio 2019, it really depends on the different versions of Visual Studio and Windows 10 SDK. And yes, if Visual Studio is installed, starting from the regular command prompt might work (the interpreter is looking in the registry to find the needed directories).

P.S. And here is the result of the nigtly tests with ROOT v6.24 on Windows:
root-v6-24-test-results.txt (390.2 KB)

All these things work on Linux/Mac, what are specifically the errors you see?

Thanks @etejedor ! So @Salomon it might well be a Windows limitation. If it’s the case, feel free to open issues at at Issues · root-project/web · GitHub . We will look at them as soon as we can (but note that due to priority changes, the delay might be quite long)

This topic was automatically closed 14 days after the last reply. New replies are no longer allowed.