Thread: [Quantlib-users] Error in building Python wheel

Hi 
I have been trying to build the Python wheel as advised on 
https://www.quantlib.org/install/windows-python.shtml 
I used latest Quantlib 1.41 and Quantlib-SWIG 1.41 as well.
1) I set up the environment variables 


2) This works fine 

3) I get an error message which I have attached in Error.txt but its along the line of incompatible Quantlib /SWIG versions as some of the below have been deprecated.
C:\local\QuantLib-SWIG-1.41\Python>python -m build --wheel --no-isolation


Any help pls ?Thank you Chirag

 Hi AllI built Quantlib with the newfxforward.hpp, fxforward.cpp , fxforwarddiscountingengine hpp.cpp which I had recently contributed and successfullyin my own version of Quantlib 1.41. All tests work


I placed my fxforward.i file andswig runs successfully



The wheel is generated successfully



I am able to pip install the wheeland successfully can “import Quantlib as ql” and also can run certain Pythonfiles under SWIG in Examples and Tests (european-option.py,test_blackformula.py)

For some reason my FX Forward testsall fail. (attached test_fxforward.py)

How do I check if my FXForward classwas successfully exposed to the Python API ? If any tools available ?

When I do ql.  there is no dropdown either in IDE like VSCodeto see what ql functions are being exposed in Python ?

Thank you all 

 

Hi Chirag, did you add your fxforward.i to the files included in ql.i ?

Luigi


On Fri, Mar 13, 2026 at 7:42 AM Chirag Desai <chi...@ya...>
wrote:

> Hi All
> I built Quantlib with the new fxforward.hpp, fxforward.cpp ,
> fxforwarddiscountingengine hpp.cpp which I had recently contributed and
> successfully in my own version of Quantlib 1.41. All tests work
>
> I placed my fxforward.i file and swig runs successfully
>
> The wheel is generated successfully
>
> I am able to pip install the wheel and successfully can “import Quantlib
> as ql” and also can run certain Python files under SWIG in Examples and
> Tests (european-option.py, test_blackformula.py)
>
> For some reason my FX Forward tests all fail. (attached test_fxforward.py)
>
> How do I check if my FXForward class was successfully exposed to the
> Python API ? If any tools available ?
>
> When I do ql.  there is no dropdown either in IDE like VSCode to see what
> ql functions are being exposed in Python ?
>
> Thank you all
>
>
>
>
>

 Thank you Mr Luigi
1) I added in ql.i and recompiled Quantlib as well
2) I get error messages now when building the wheel stating FXForward class cannot be found. I have attached the error messages.
Build was successful 





    On Friday, March 13, 2026 at 10:50:47 PM GMT+8, Luigi Ballabio <lui...@gm...> wrote:  
 
 Hi Chirag, did you add your fxforward.i to the files included in ql.i ?
Luigi

On Fri, Mar 13, 2026 at 7:42 AM Chirag Desai <chi...@ya...> wrote:

 Hi AllI built Quantlib with the newfxforward.hpp, fxforward.cpp , fxforwarddiscountingengine hpp.cpp which I had recently contributed and successfullyin my own version of Quantlib 1.41. All tests work


I placed my fxforward.i file andswig runs successfully



The wheel is generated successfully



I am able to pip install the wheeland successfully can “import Quantlib as ql” and also can run certain Pythonfiles under SWIG in Examples and Tests (european-option.py,test_blackformula.py)

For some reason my FX Forward testsall fail. (attached test_fxforward.py)

How do I check if my FXForward classwas successfully exposed to the Python API ? If any tools available ?

When I do ql.  there is no dropdown either in IDE like VSCodeto see what ql functions are being exposed in Python ?
Thank you all
 




  

Your new class is not in QuantLib 1.41.  You need to check out the latest
versions of QuantLib and QuantLib-SWIG from GitHub and use those ones.

Luigi


On Sat, Mar 14, 2026 at 5:41 AM Chirag Desai <chi...@ya...>
wrote:

> Thank you Mr Luigi
>
> 1) I added in ql.i and recompiled Quantlib as well
>
> 2) I get error messages now when building the wheel stating FXForward
> class cannot be found. I have attached the error messages.
>
> Build was successful
> [image: Inline image]
>
> [image: Inline image]
>
>
>
> On Friday, March 13, 2026 at 10:50:47 PM GMT+8, Luigi Ballabio <
> lui...@gm...> wrote:
>
>
> Hi Chirag, did you add your fxforward.i to the files included in ql.i ?
>
> Luigi
>
>
> On Fri, Mar 13, 2026 at 7:42 AM Chirag Desai <chi...@ya...>
> wrote:
>
> Hi All
> I built Quantlib with the new fxforward.hpp, fxforward.cpp ,
> fxforwarddiscountingengine hpp.cpp which I had recently contributed and
> successfully in my own version of Quantlib 1.41. All tests work
>
> I placed my fxforward.i file and swig runs successfully
>
> The wheel is generated successfully
>
> I am able to pip install the wheel and successfully can “import Quantlib
> as ql” and also can run certain Python files under SWIG in Examples and
> Tests (european-option.py, test_blackformula.py)
>
> For some reason my FX Forward tests all fail. (attached test_fxforward.py)
>
> How do I check if my FXForward class was successfully exposed to the
> Python API ? If any tools available ?
>
> When I do ql.  there is no dropdown either in IDE like VSCode to see what
> ql functions are being exposed in Python ?
> Thank you all
>
>
>
>
>
>

 Hi Luigi
I am very sorry but may not have been clear enough
1) I got the latest versions of Quantlib 1.41 and Quantlib-SWIG 1.412) I manually added the FXForward class in my local version and it builds fine and the test for it under testsuite works fine3) I added the fxforward.i and amended ql.i4) When I build the python wheel it cannot find the FX Forward class
(When I do the above exercise without the FX Forward class, I can build the wheel successfully and all works well)


    On Sunday, March 15, 2026 at 12:33:03 AM GMT+8, Luigi Ballabio <lui...@gm...> wrote:  
 
 Your new class is not in QuantLib 1.41.  You need to check out the latest versions of QuantLib and QuantLib-SWIG from GitHub and use those ones.
Luigi

On Sat, Mar 14, 2026 at 5:41 AM Chirag Desai <chi...@ya...> wrote:

 Thank you Mr Luigi
1) I added in ql.i and recompiled Quantlib as well
2) I get error messages now when building the wheel stating FXForward class cannot be found. I have attached the error messages.
Build was successful 





    On Friday, March 13, 2026 at 10:50:47 PM GMT+8, Luigi Ballabio <lui...@gm...> wrote:  
 
 Hi Chirag, did you add your fxforward.i to the files included in ql.i ?
Luigi

On Fri, Mar 13, 2026 at 7:42 AM Chirag Desai <chi...@ya...> wrote:

 Hi AllI built Quantlib with the newfxforward.hpp, fxforward.cpp , fxforwarddiscountingengine hpp.cpp which I had recently contributed and successfullyin my own version of Quantlib 1.41. All tests work


I placed my fxforward.i file andswig runs successfully



The wheel is generated successfully



I am able to pip install the wheeland successfully can “import Quantlib as ql” and also can run certain Pythonfiles under SWIG in Examples and Tests (european-option.py,test_blackformula.py)

For some reason my FX Forward testsall fail. (attached test_fxforward.py)

How do I check if my FXForward classwas successfully exposed to the Python API ? If any tools available ?

When I do ql.  there is no dropdown either in IDE like VSCodeto see what ql functions are being exposed in Python ?
Thank you all
 




  
  

Hello Chirag,
    please don't use the latest 1.41.  Backporting your class manually
might skip some steps.  Use a checkout from the latest master from GitHub,
where your FxForward is already included correctly.  Use a checkout for the
SWIG part too; you'll have to do that anyway in order to open a pull
request.

Luigi


On Mon, Mar 16, 2026 at 8:53 AM Chirag Desai <chi...@ya...>
wrote:

> Hi Luigi
>
> I am very sorry but may not have been clear enough
>
> 1) I got the latest versions of Quantlib 1.41 and Quantlib-SWIG 1.41
> 2) I manually added the FXForward class in my local version and it builds
> fine and the test for it under testsuite works fine
> 3) I added the fxforward.i and amended ql.i
> 4) When I build the python wheel it cannot find the FX Forward class
>
> (When I do the above exercise without the FX Forward class, I can build
> the wheel successfully and all works well)
>
> [image: Inline image]
>
> On Sunday, March 15, 2026 at 12:33:03 AM GMT+8, Luigi Ballabio <
> lui...@gm...> wrote:
>
>
> Your new class is not in QuantLib 1.41.  You need to check out the latest
> versions of QuantLib and QuantLib-SWIG from GitHub and use those ones.
>
> Luigi
>
>
> On Sat, Mar 14, 2026 at 5:41 AM Chirag Desai <chi...@ya...>
> wrote:
>
> Thank you Mr Luigi
>
> 1) I added in ql.i and recompiled Quantlib as well
>
> 2) I get error messages now when building the wheel stating FXForward
> class cannot be found. I have attached the error messages.
>
> Build was successful
> [image: Inline image]
>
> [image: Inline image]
>
>
>
> On Friday, March 13, 2026 at 10:50:47 PM GMT+8, Luigi Ballabio <
> lui...@gm...> wrote:
>
>
> Hi Chirag, did you add your fxforward.i to the files included in ql.i ?
>
> Luigi
>
>
> On Fri, Mar 13, 2026 at 7:42 AM Chirag Desai <chi...@ya...>
> wrote:
>
> Hi All
> I built Quantlib with the new fxforward.hpp, fxforward.cpp ,
> fxforwarddiscountingengine hpp.cpp which I had recently contributed and
> successfully in my own version of Quantlib 1.41. All tests work
>
> I placed my fxforward.i file and swig runs successfully
>
> The wheel is generated successfully
>
> I am able to pip install the wheel and successfully can “import Quantlib
> as ql” and also can run certain Python files under SWIG in Examples and
> Tests (european-option.py, test_blackformula.py)
>
> For some reason my FX Forward tests all fail. (attached test_fxforward.py)
>
> How do I check if my FXForward class was successfully exposed to the
> Python API ? If any tools available ?
>
> When I do ql.  there is no dropdown either in IDE like VSCode to see what
> ql functions are being exposed in Python ?
> Thank you all
>
>
>
>
>
>

It looks like you're not using QuantLib 1.41 (the release you find at <
https://github.com/lballabio/QuantLib/releases/tag/v1.41> but a checkout of
the git repository, which is more recent than 1.41 and removed a few
deprecated classes.  If that's the case, you also need a checkout of the
git repository for QuantLib-SWIG.

Luigi


On Wed, Mar 11, 2026 at 12:38 PM Chirag Desai <chi...@ya...>
wrote:

> Hi
>
> I have been trying to build the Python wheel as advised on
>
> https://www.quantlib.org/install/windows-python.shtml
>
> I used latest Quantlib 1.41 and Quantlib-SWIG 1.41 as well.
>
> 1) I set up the environment variables
>
> [image: Inline image]
>
> 2) This works fine
> [image: Inline image]
>
> 3) I get an error message which I have attached in Error.txt but its along
> the line of incompatible Quantlib /SWIG versions as some of the below have
> been deprecated.
>
> C:\local\QuantLib-SWIG-1.41\Python>python -m build --wheel --no-isolation
>
> [image: Inline image]
> Any help pls ?
> Thank you
> Chirag
>
>
>
>
>
>