Re: [C++-sig] Accessing 2D array from python in C++
Hi Jim,
Do you mean, "you could wrap multi_array itself using class_", I should do as
below:
boost::python::class_ >
>("PyVec").def(boost::python::vector_indexing_suite
> >());
I also did as below to expose the data from python to C++:
main_namespace["Vp"] = boost::python::ptr(&Vp_cpp);
However, when I try to access the data to the std::cout, like the following, it
complains:
std::cout << "Vp_cpp = " << Vp_cpp << std::endl;
What could be wrong or am I missing something? Thanks in advance.
From: Jim Bosch
To: Development of Python/C++ integration ; shahmi
Sent: Tuesday, August 14, 2012 5:54 PM
Subject: Re: [C++-sig] Accessing 2D array from python in C++
On Aug 14, 2012 4:25 AM, "shahmi" wrote:
>
> Hi,
>
> I have tried to access/expose 2D array from python in C++ using
> boost::multi_array. Nevertheless, it seems that the
> boost::multi_array datatype is not supported. Is there any way to
> resolve this? My way of accessing it as below:
>
> boost::python::object Vp = main_namespace["Vp"];
> Vp_cpp = boost::python::extract 2> >(Vp);
>
> I've also tried to try to use 2D vector as below, nonetheless, it still
> doesn't work:
>
> boost::python::object Vp = main_namespace["Vp"];
> Vp_cpp = boost::python::extract >
> >(Vp);
>
> The error message I received is "TypeError: No registered converter was able
> to produce a C++ rvalue of type std::vector std::allocator >, std::allocator std::allocator > > > from this Python object of type matrix"
>
In general Boost.Python doesn't provide converters for all the other boost
libraries.
The first question is what you want to return in Python; you could wrap
multi_array itself using class_. You could also return a nested list or tuple.
If you want to use numpy, you'll probably want a helper library like this one:
https://github.com/ndarray/Boost.NumPy
In either of the last two cases, you can either write your own converter and
add it to the converter registry (harder, but reusable), or write a custom
wrapper for the function that returns a 2-d array (easier, but not good if
you have many such functions).
HTH
Jim___
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Re: [C++-sig] Accessing 2D array from python in C++
I apologize for double posting this because it was spammed before.
Hi Jim,
Do you mean, "you could wrap multi_array itself using class_", I should do as
below:
boost::python::class_ >
>("PyVec").def(boost::python::vector_indexing_suite
> > >());
I also did as below to expose the data from python to C++:
main_namespace["Vp"] = boost::python::ptr(&Vp_cpp);
However, when I try to access the data to the std::cout, like the following, it
complains:
std::cout << "Vp_cpp = " << Vp_cpp << std::endl;
What could be wrong or am I missing something? Thanks in advance.
From: Jim Bosch
To: Development of Python/C++ integration ; shahmi
Sent: Tuesday, August 14, 2012 5:54 PM
Subject: Re: [C++-sig] Accessing 2D array from python in C++
On Aug 14, 2012 4:25 AM, "shahmi" wrote:
>
> Hi,
>
> I have tried to access/expose 2D array from python in C++ using
> boost::multi_array. Nevertheless, it seems that the
> boost::multi_array datatype is not supported. Is there any way to
> resolve this? My way of accessing it as below:
>
> boost::python::object Vp = main_namespace["Vp"];
> Vp_cpp = boost::python::extract 2> >(Vp);
>
> I've also tried to try to use 2D vector as below, nonetheless, it still
> doesn't work:
>
> boost::python::object Vp = main_namespace["Vp"];
> Vp_cpp = boost::python::extract >
> >(Vp);
>
> The error message I received is "TypeError: No registered converter was able
> to produce a C++ rvalue of type std::vector std::allocator >, std::allocator std::allocator > > > from this Python object of type matrix"
>
In general Boost.Python doesn't provide converters for all the other boost
libraries.
The first question is what you want to return in Python; you could wrap
multi_array itself using class_. You could also return a nested list or tuple.
If you want to use numpy, you'll probably want a helper library like this one:
https://github.com/ndarray/Boost.NumPy
In either of the last two cases, you can either write your own converter and
add it to the converter registry (harder, but reusable), or write a custom
wrapper for the function that returns a 2-d array (easier, but not good if
you have many such functions).
HTH
Jim___
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Cplusplus-sig@python.org
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[C++-sig] Fw: Accessing 2D array from python in C++
- Forwarded Message -
From: alfa
To: Jim Bosch ; Development of Python/C++ integration
Sent: Wednesday, August 15, 2012 10:57 AM
Subject: Re: [C++-sig] Accessing 2D array from python in C++
I apologize for double posting this because it was spammed before.
Hi Jim,
Do you mean, "you could wrap multi_array itself using class_", I should do as
below:
boost::python::class_ >
>("PyVec").def(boost::python::vector_indexing_suite
> > >());
I also did as below to expose the data from python to C++:
main_namespace["Vp"] = boost::python::ptr(&Vp_cpp);
However, when I try to access the data to the std::cout, like the following, it
complains:
std::cout << "Vp_cpp = " << Vp_cpp << std::endl;
What could be wrong or am I missing something? Thanks in advance.
From: Jim Bosch
To: Development of Python/C++ integration ; shahmi
Sent: Tuesday, August 14, 2012 5:54 PM
Subject: Re: [C++-sig] Accessing 2D array from python in C++
On Aug 14, 2012 4:25 AM, "shahmi" wrote:
>
> Hi,
>
> I have tried to access/expose 2D array from python in C++ using
> boost::multi_array. Nevertheless, it seems that the
> boost::multi_array datatype is not supported. Is there any way to
> resolve this? My way of accessing it as below:
>
> boost::python::object Vp = main_namespace["Vp"];
> Vp_cpp = boost::python::extract 2> >(Vp);
>
> I've also tried to try to use 2D vector as below, nonetheless, it still
> doesn't work:
>
> boost::python::object Vp = main_namespace["Vp"];
> Vp_cpp = boost::python::extract >
> >(Vp);
>
> The error message I received is "TypeError: No registered converter was able
> to produce a C++ rvalue of type std::vector std::allocator >, std::allocator std::allocator > > > from this Python object of type matrix"
>
In general Boost.Python doesn't provide converters for all the other boost
libraries.
The first question is what you want to return in Python; you could wrap
multi_array itself using class_. You could also return a nested list or tuple.
If you want to use numpy, you'll probably want a helper library like this one:
https://github.com/ndarray/Boost.NumPy
In either of the last two cases, you can either write your own converter and
add it to the converter registry (harder, but reusable), or write a custom
wrapper for the function that returns a 2-d array (easier, but not good if
you have many such functions).
HTH
Jim
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[C++-sig] Problem exposing 2D python array in C++
Hi,
Is the following way valid to expose a 2D array variable from python (Vp) to
c++(Vp_cpp)?
std::vector > Vp_cpp;
boost::python::class_ >
>("PyVec").def(boost::python::vector_indexing_suite
> >());
main_namespace["Vp"] = boost::python::ptr(&Vp_cpp);
But, then if I tried to manipulate the 2D vector in C++ like the following, it
doesn't work:
Vp_cpp[1][1] = 999;
std::cout << "Vp_cpp[1][1] = " << Vp_cpp[1][1] << std::endl; // It doesn't
print to
What could be wrong or am I missing something?
Thanks in advance.___
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[C++-sig] Exposing 2D python array in C++
Hi,
Is the following way valid to expose a 2D array variable from python (Vp) to
c++(Vp_cpp)?
std::vector > Vp_cpp;
boost::python::class_ >
>("PyVec").def(boost::python::vector_indexing_suite
> > >());
main_namespace["Vp"] = boost::python::ptr(&Vp_cpp);
But, then if I tried to manipulate the 2D vector in C++ like the following, it
doesn't work:
Vp_cpp[1][1] = 999;
std::cout << "Vp_cpp[1][1] = " << Vp_cpp[1][1] << std::endl; // It doesn't
print to
What could be wrong or am I missing something?
Thanks in advance.___
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Cplusplus-sig@python.org
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Re: [C++-sig] Accessing 2D array from python in C++
On Aug 15, 2012 1:57 AM, "alfa" wrote:
>
> I apologize for double posting this because it was spammed before.
>
> Hi Jim,
>
> Do you mean, "you could wrap multi_array itself using class_", I should
do as below:
>
> boost::python::class_ >
>("PyVec").def(boost::python::vector_indexing_suite
> >());
>
No, I don't think that will work; I meant something like this:
boost::python::class_< boost::multi_array<...> >(...)
...;
Where the last "..." is where you have to manually wrap the features of
multi_array you want to use. I'm afraid there's nothing as easy as
vector_indexing_suite.
Jim
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