Develop Reference

How to build a 32 bits version of a Python 3RD PARTY LIBRARY on my Win10 64 bits PC for a target machine running a 32 bits interpreter?

I need to package a Python library for someone using a Python 3.6.x 32 bits version so that he can pip install it. He can't change his Python interpreter so switching to 64 bits won't be possible to do.
Part of the library is written in C so compilation is needed because binaries for his Win32 3.6 interpreter version aren't available from the internet.
I'm on a Win10 64 bits machine. How can I compile and build a 32 bits version of the lib he could then install on his machine? Is there a pip command to do so? I Have MSVC build tools installed on my machine (2015-2022 x64 and x86).
Thanks in advance :)

In terms of the C code...
From here: https://docs.python.org/3/distutils/builtdist.html
python setup.py build --plat-name=win-amd64
So I'd suggest trying
--plat-name=win32

How do I explicitly install and launch the 64-bit version of Python after installing the Python.org distribution?

I just installed the latest version of Python from enter link description here. I expected the installer to query my CPU at installion time and install the a 64-bit version by default, since my CPU machine is 64-bit Intel version.
After installation, I am a unclear by the version data that shows in IDLE when I start Python:
Python 3.8.2 (tags/v3.8.2:7b3ab59, Feb 25 2020, 22:45:29) [MSC v.1916 32 bit (Intel)] on win32
I want to use highest performance Python for machine learning, database, and number crunching applications.
There is no "64-bit only" version on Python.org website. The only kit available is named Windows x86-64 executable installer Windows for AMD64/EM64T/x64.
Does the Python installer install both the 32-bit and 64-bit API? This is not reflected in the version information that is displayed.
Am I asking the wrong question, because the 64-bit and 32-bit APIs are both installed, and just the version displayed is not complete? How does Windows or Python know to switch to the 64-bit API for libraries like Numpy, Numba, etc. that work best with 64-bit code?
Is there a way to explicitly start the 64-bit version?
When should I do this explicitly versus letting Windows launch the default 32-bit version?

you should only download and install the Windows x86-64 executable installer Windows for AMD64/EM64T/x64. if you want 64bit. However do NOT expect python to be super fast, as a dynamic typing language, it will be at least 100 times slower than static typing language such as C/C++ or Java.
If you want your numpy/pandas/sklearn to be as fast as possible, you should focus on optimizing your workflow, don't commit to unnecessary task. Or you can check out intel's python distribution if you're on Intel CPU. Or explore other multi-process pandas solution when on a multi-core AMD cpu.

Scipy on Python 3.5 - manual installation

I downloaded scipy-0.16.1-win32-superpack-python3.4.exe and tried to install it on WinServer 2008 R2 64bit with Python 3.5 preinstalled. SciPy returns error saying that Python 3.4 not found. My server does not have Internet connection, so I have to download and move files manually. Any suggestions? Should I just try to downgrade to Python 3.4? Is it easy to downgrade?

Christoph Gohlke's binaries for Python on Windows are a godsend when you need to install a package that requires a C compiler, like numpy or scipy, though he only tends to host binaries for the latest versions of the packages (but for all current versions of CPython).
When installing these binaries, make sure that the platform on the binary (usually win32 or win_amd64) matches the type of Python you installed (32-bit or 64-bit), and note that it may not match your OS's bit-ness if you installed a 32-bit version of Python on a 64-bit OS.
Since you apparently have a 64-bit version of Python 3.5 installed, the wheel you want is scipy‑0.16.1‑cp35‑none‑win_amd64.whl.

Conda build a 32 bit package on a 64 bit machine

I have been using conda as a package manager for a lot of my work and its really helped keep the environments of multiple people in check with both Python and binary packages. Its been all sunshine and rainbows while all of my users have been on 64-bit Linux machines.
Now I need to support a handful of 32-bit machines. Is there any way to build 32-bit versions of my packages on my 64-bit machine?
I've found this answer on SO, How to compile a 32-bit binary on a 64-bit linux machine with gcc/cmake but I can't figure out how to get it to compile and upload both 32 and 64 bit versions.

conda assumes that the entire installation is 64-bit, so the first thing you'll need to do is create a separate Miniconda installation for 32-bit building. Then build your recipe. If the package links against any system libraries, you'll need to have the 32-bit versions installed. I personally find it easiest to build 32-bit packages on a 32-bit VM, as then you know that everything is 32-bit, but building on a 64-bit machine is possible and it should work (although I would recommend testing the package on a 32-bit machine).

Installation of pygtk not working

I am running on Windows (64bit version) and have python 2.7 (also 64 bit) installed. I downloaded the all-in-one installer for pygtk for python 2.7, but when I run it, it shows "python 2.7 could not be located on your system". Why is it so when I already have python 2.7 installed?

Currently, the all-in-one installer binaries here are compiled against 32 bits python only. There is no 64 bits binary in there. Install python 2.7 32 bits on your windows and it should work.
Alternatively, you could grab a C compiler, and then try to compile the installer sources. That's a lot harder though.

Did you install a 64bit Python interpreter? The most probable reason
for that message is that the all-in-one installer can't locate a 32bit
Python interpreter (which works fine on 64bit Windows).
http://permalink.gmane.org/gmane.comp.gnome.gtk+.python/15263