Why installed libtorrent shows Import Error?

I have built libtorrent with boost with this commands in the boost root folder :

bootstrap.bat
b2 --hash cxxstd=14 release

and after I have added BOOST_ROOT and BOOST_BUILD_PATH to PATH variable.

I also have downloaded OpenSSL and build it then have copied to Visual studio 15 2017 compiler include and libs folder repectively.

Next in the libtorrent root folder I have run this commands:

b2 variant=release link=shared
b2 install --prefix=build

The build was successful and libtorrent c++ library has created.

and after that I have run these commands :

py setup.py build
py setup.py install

They executed with no errors and libtorrent installed in my python libs/site-packages folder. But when I import it this error shows:

Python Import Error []

What build steps might I have done wrong?

Os : Windows 10 x64

Python : 3.9.5 x64

Libtorrent : 2.0.5

Boost : 1.78.0

I have followed from the libtorrent docs : https://libtorrent.org/building.html and https://www.libtorrent.org/python_binding.html

I found the answer.

While building libtorrent python binding 2 factors are important:

1- openSSL version 2- linking type

1. python comes with openssl v.1.1 (or similar based on python version) , if building python binding with openssl v.1.1 (which is the latest version while I am writing) one dependency solved otherwise, if using openssl v.3 for building 2 dependency must add to python which they are:

// 32 or 64 bits library based on openssl build

libssl-3-x64.dll
libcrypto-3-x64.dll

2 ) in the time of building python binding 2 commands can be use:

a ) simple with default parameters :

py setup.py build
py setup.py install

In this case in default libtorrent and boost-python linking static.

b ) complex one with more control (I think) :

py setup.py build_ext --b2-args="VARS" install

In the VARS place we can write boost build options but these are the one we want:

libtorrent-link=TYPE  boost-link= TYPE

TYPE can be static or shared but anyone that sets shared , it becomes dependency. two files which is in need are :

// 32 and 64 bits file may have different name
// files can have different names but they are similar to below

torrent-rastarbar.dll
boost_python(PYTHON-VERSION)(SOME-INFO).dll

boost python can be find in the boost root directory in the stage/lib .

pleae note that you must build boost and libtorrent SHARED for this solution.

Conclusion :

as mentioned above these dependency must add to based on the build setting you did:

1 - OpenSSL libraries 2 - Boost python 3 - libtorrent libraries

There is an optional file that mentioned in some forums and discussion msvcr90.dll which does not effect on my project but good to point.

Put those files to a directory which can be find by python interpreter or put in project your folder and add this piece of code before imporing libtorrent :

import os

current_path = os.path.abspath(".")

# do not pass relative path like ".", pass full path

os.add_dll_directory(current_path)

Sorry for any poor english. :)