PyQtBuilder and Python from source on Windows

Patrick Stinson patrickkidd at
Mon Oct 5 07:46:44 BST 2020

Maybe this is because sip is not handling the paths correctly?

Here is the first failing args to cl.exe. Note the paths returned from distutils.sysconfig.get_python_inc() are correct but sip doesn’t separate them on the ‘;’ token, and then maybe also doesn’t use the correct os.sep?

cl -c -nologo -Zc:wchar_t -FS -Zc:strictStrings -O2 -MD -W3 -w44456 -w44457 -w44458 -DUNICODE -D_UNICODE -DWIN32 -D_ENABLE_EXTENDED_ALIGNED_STORAGE -DWIN64 -DPy_LIMITED_API=0x03040000 -DNDEBUG -DQT_NO_EXCEPTIONS -DQT_NO_DEBUG -DQT_PLUGIN -D_WINDLL -I. -I. -I.. -IC:/familydiagram/vendor/sysroot-dev/Python-3.7.8/include;C:/familydiagram/vendor/sysroot-dev/Python-3.7.8/PC -IC:\familydiagram\vendor\sysroot-dev\Qt-5.15.1\mkspecs\win32-msvc -Forelease\ @C:\Users\patrick\AppData\Local\Temp\nm1BE7.tmp

> On Oct 4, 2020, at 10:43 PM, Patrick Stinson <patrickkidd at> wrote:
> sip-build for PyQt5 fails to find Python.h with Python [3.7.8] built from source on Windows [10]. I imagine this has to do with how the python source seems to have no notion of an install prefix on Windows and leaves binaries in the build dir.
> Is there any way to specify include dirs and probably also lib dirs to sip-build for PyQt5? Python headers are in <PY_SOURCE>\include and <PY_SOURCE>\PC.
> -Patrick

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