# Python pass parameter as const \*gr\_complex? **URL:** \ **Category:** GNU Radio\ **Created:** [January 7, 2015, 2:50pm UTC](https://www.ruby-forum.com/t/python-pass-parameter-as-const-gr-complex/233739 "2015-01-07T14:50:40Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![addis\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/c4cdca/32.png) [@addis\_a](https://www.ruby-forum.com/u/addis_a)\ **Post date:** [January 7, 2015, 2:50pm UTC](https://www.ruby-forum.com/t/python-pass-parameter-as-const-gr-complex/233739/1 "2015-01-07T14:50:40Z")
Hi list, I am trying to use the gr::digital::constellation::decision\_maker(.) method from python, but I get an error message. In order to reproduce call in python: import gnuradio.digital a = gnuradio.digital.constellation\_qpsk() b = complex(1+1j) a.decision\_maker(b) =\> TypeError […] argument 2 of type ‘gr\_complex const\*’ The C+±implementation is wrapped by SWIG, where the error occurs. This might be a silly question, but what am I doing wrong? Thanks for any help. Best regards Stephan Ludwig Robert Bosch GmbH Corporate Sector Research & Advance Engineering, Communication Technology (CR/AEH4) Renningen 70465 Stuttgart GERMANY [www.bosch.com](http://www.bosch.com)[http://www.bosch.com](http://www.bosch.com) Tel. +49(711)811-8809 Fax +49(711)811-1052 Mobile +49(172)5630639 removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) Registered Office: Stuttgart, Registration Court: Amtsgericht Stuttgart, HRB 14000; Chairman of the Supervisory Board: Franz Fehrenbach; Managing Directors: Dr. Volkmar Denner, Dr. Stefan Asenkerschbaumer, Dr. Rolf Bulander, Dr. Stefan Hartung, Dr. Dirk Hoheisel, Christoph Kbel, Uwe Raschke, Wolf-Henning Scheider, Dr. Werner Struth, Peter Tyroller ---
**Author:** ![Ludwig\_Stephan\_SCR](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/e36b37/32.png) [@Ludwig\_Stephan\_SCR](https://www.ruby-forum.com/u/Ludwig_Stephan_SCR)\ **Post date:** [January 20, 2015, 3:58pm UTC](https://www.ruby-forum.com/t/python-pass-parameter-as-const-gr-complex/233739/2 "2015-01-20T15:58:24Z")
On Wed, Jan 7, 2015 at 7:57 AM, Ludwig Stephan (CR/AEH4) \< [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)\> wrote: > =\> TypeError [..] argument 2 of type ‘gr\_complex const\*’ > The C+±implementation is wrapped by SWIG, where the error occurs. > > This might be a silly question, but what am I doing wrong? > > Thanks for any help. > > Best regards > > _Stephan Ludwig_ Hi Stephan, You’re not doing anything wrong per se, but the block isn’t really meant to be used that way. SWIG needs to be told how to handle some types of argument formats, and it hasn’t been told how to handle this one. The post 3.7 way we’ve been handling SWIG is to just include the public .h file as the interface, so all methods are exported into SWIG. A class like this needs that method to be public for use as a contained object in the block that calls it, but it’s not really meant for use outside like this. Not that it couldn’t be, but you’d have to work with SWIG to let it understand how to call that function with the proper input type. Tom ---
**Author:** ![Ludwig\_Stephan\_SCR](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/e36b37/32.png) [@Ludwig\_Stephan\_SCR](https://www.ruby-forum.com/u/Ludwig_Stephan_SCR)\ **Post date:** [January 21, 2015, 9:14am UTC](https://www.ruby-forum.com/t/python-pass-parameter-as-const-gr-complex/233739/3 "2015-01-21T09:14:42Z")
Thank you, Tom, for your enlightening answer. Please let me ask two additional questions: 1. If I understood your explanation correctly, as a consequence of this, one could not use the decision\_maker method within a block, which is coded solely in python. Right? 2. Isn’t “const gr\_complex\*” a type, which is used very often in the block I/O interfaces, and shouldn’t, thus, the GR configuration of SWIG already let it know how to translate python/complex to gr\_complex? Best regards Stephan Ludwig Robert Bosch GmbH Corporate Sector Research & Advance Engineering, Communication Technology (CR/AEH4) Renningen 70465 Stuttgart GERMANY > **[Want to know how to live #LikeABosch?](https://www.bosch.com/)** > > Moving stories and inspiring interviews. Experience the meaning of "invented for life" by Bosch completely new. Visit our international website. Tel. +49(711)811-8809 Fax +49(711)811-1052 Mobile +49(172)5630639 removed\_email\_address@domain.invalid Registered Office: Stuttgart, Registration Court: Amtsgericht Stuttgart, HRB 14000; Chairman of the Supervisory Board: Franz Fehrenbach; Managing Directors: Dr. Volkmar Denner, Dr. Stefan Asenkerschbaumer, Dr. Rolf Bulander, Dr. Stefan Hartung, Dr. Dirk Hoheisel, Christoph Kübel, Uwe Raschke, Wolf-Henning Scheider, Dr. Werner Struth, Peter Tyroller Von: removed\_email\_address@domain.invalid [[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)] Im Auftrag von Tom R. Gesendet: Dienstag, 20. Januar 2015 15:57 An: Ludwig Stephan (CR/AEH4) Cc: removed\_email\_address@domain.invalid Betreff: Re: [Discuss-gnuradio] Python pass parameter as const \*gr\_complex? On Wed, Jan 7, 2015 at 7:57 AM, Ludwig Stephan (CR/AEH4) [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: Hi list, I am trying to use the gr::digital::constellation::decision\_maker(.) method from python, but I get an error message. In order to reproduce call in python: import gnuradio.digital a = gnuradio.digital.constellation\_qpsk() b = complex(1+1j) a.decision\_maker(b) =\> TypeError […] argument 2 of type ‘gr\_complex const\*’ The C+±implementation is wrapped by SWIG, where the error occurs. This might be a silly question, but what am I doing wrong? Thanks for any help. Best regards Stephan Ludwig Hi Stephan, You’re not doing anything wrong per se, but the block isn’t really meant to be used that way. SWIG needs to be told how to handle some types of argument formats, and it hasn’t been told how to handle this one. The post 3.7 way we’ve been handling SWIG is to just include the public .h file as the interface, so all methods are exported into SWIG. A class like this needs that method to be public for use as a contained object in the block that calls it, but it’s not really meant for use outside like this. Not that it couldn’t be, but you’d have to work with SWIG to let it understand how to call that function with the proper input type. Tom ---
**Author:** ![Ludwig\_Stephan\_SCR](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/e36b37/32.png) [@Ludwig\_Stephan\_SCR](https://www.ruby-forum.com/u/Ludwig_Stephan_SCR)\ **Post date:** [January 21, 2015, 2:51pm UTC](https://www.ruby-forum.com/t/python-pass-parameter-as-const-gr-complex/233739/4 "2015-01-21T14:51:45Z")
On Wed, Jan 21, 2015 at 3:13 AM, Ludwig Stephan (CR/AEH4) \< [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)\> wrote: > Thank you, Tom, for your enlightening answer. Please let me ask two > additional questions: > > 1. If I understood your explanation correctly, as a consequence of this, > one could not use the decision\_maker method within a block, which is coded > solely in python. Right? Correct. > 1. Isn’t “const gr\_complex\*” a type, which is used very often in the block > I/O interfaces, and shouldn’t, thus, the GR configuration of SWIG already > let it know how to translate python/complex to gr\_complex? No. That type is almost never used. What is often used is “const std::vector\”. But again, this class was designed to be called from within a block’s work function, so the data structure would have already been a “const gr\_complex\*” (casting the input\_items argument). Tom ---
**Author:** ![Ludwig\_Stephan\_SCR](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/e36b37/32.png) [@Ludwig\_Stephan\_SCR](https://www.ruby-forum.com/u/Ludwig_Stephan_SCR)\ **Post date:** [January 21, 2015, 4:27pm UTC](https://www.ruby-forum.com/t/python-pass-parameter-as-const-gr-complex/233739/5 "2015-01-21T16:27:41Z")
Hi Tom, thank you for clarification. The problem arose, when I wanted to use the method from within a _python_block’s work function. But I understood, that this is not possible (a.t.m.), and I will write a C++ clock, which should perform better anyways 😉 Best regards Stephan Ludwig Robert Bosch GmbH Corporate Sector Research & Advance Engineering, Communication Technology (CR/AEH4) Renningen 70465 Stuttgart GERMANY [www.bosch.com](http://www.bosch.com)[http://www.bosch.com](http://www.bosch.com) Tel. +49(711)811-8809 Fax +49(711)811-1052 Mobile +49(172)5630639 removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) Registered Office: Stuttgart, Registration Court: Amtsgericht Stuttgart, HRB 14000; Chairman of the Supervisory Board: Franz Fehrenbach; Managing Directors: Dr. Volkmar Denner, Dr. Stefan Asenkerschbaumer, Dr. Rolf Bulander, Dr. Stefan Hartung, Dr. Dirk Hoheisel, Christoph Kübel, Uwe Raschke, Wolf-Henning Scheider, Dr. Werner Struth, Peter Tyroller Von: removed\_email\_address@domain.invalid [[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)] Im Auftrag von Tom R. Gesendet: Mittwoch, 21. Januar 2015 14:50 An: Ludwig Stephan (CR/AEH4) Cc: removed\_email\_address@domain.invalid Betreff: Re: [Discuss-gnuradio] Python pass parameter as const \*gr\_complex? On Wed, Jan 21, 2015 at 3:13 AM, Ludwig Stephan (CR/AEH4) \ wrote: Thank you, Tom, for your enlightening answer. Please let me ask two additional questions: 1. If I understood your explanation correctly, as a consequence of this, one could not use the decision\_maker method within a block, which is coded solely in python. Right? Correct. 1. Isn’t “const gr\_complex\*” a type, which is used very often in the block I/O interfaces, and shouldn’t, thus, the GR configuration of SWIG already let it know how to translate python/complex to gr\_complex? No. That type is almost never used. What is often used is “const std::vector\”. But again, this class was designed to be called from within a block’s work function, so the data structure would have already been a “const gr\_complex\*” (casting the input\_items argument). Tom Best regards Stephan Ludwig Robert Bosch GmbH Corporate Sector Research & Advance Engineering, Communication Technology (CR/AEH4) Renningen 70465 Stuttgart GERMANY [www.bosch.com](http://www.bosch.com)[http://www.bosch.com](http://www.bosch.com) Tel. +49(711)811-8809tel:%2B49(711)811-8809 Fax +49(711)811-1052tel:%2B49(711)811-1052 Mobile +49(172)5630639tel:%2B49(172)5630639 removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) Registered Office: Stuttgart, Registration Court: Amtsgericht Stuttgart, HRB 14000; Chairman of the Supervisory Board: Franz Fehrenbach; Managing Directors: Dr. Volkmar Denner, Dr. Stefan Asenkerschbaumer, Dr. Rolf Bulander, Dr. Stefan Hartung, Dr. Dirk Hoheisel, Christoph Kübel, Uwe Raschke, Wolf-Henning Scheider, Dr. Werner Struth, Peter Tyroller Von: removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) [[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)] Im Auftrag von Tom R. Gesendet: Dienstag, 20. Januar 2015 15:57 An: Ludwig Stephan (CR/AEH4) Cc: removed\_email\_address@domain.invalid[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) Betreff: Re: [Discuss-gnuradio] Python pass parameter as const \*gr\_complex? On Wed, Jan 7, 2015 at 7:57 AM, Ludwig Stephan (CR/AEH4) \ wrote: Hi list, I am trying to use the gr::digital::constellation::decision\_maker(.) method from python, but I get an error message. In order to reproduce call in python: import gnuradio.digital a = gnuradio.digital.constellation\_qpsk() b = complex(1+1j) a.decision\_maker(b) =\> TypeError […] argument 2 of type ‘gr\_complex const\*’ The C+±implementation is wrapped by SWIG, where the error occurs. This might be a silly question, but what am I doing wrong? Thanks for any help. Best regards Stephan Ludwig Hi Stephan, You’re not doing anything wrong per se, but the block isn’t really meant to be used that way. SWIG needs to be told how to handle some types of argument formats, and it hasn’t been told how to handle this one. The post 3.7 way we’ve been handling SWIG is to just include the public .h file as the interface, so all methods are exported into SWIG. A class like this needs that method to be public for use as a contained object in the block that calls it, but it’s not really meant for use outside like this. Not that it couldn’t be, but you’d have to work with SWIG to let it understand how to call that function with the proper input type. Tom