How to redirect output of nanobind::print

[Rxphi]

Hello, I am working on my first project which uses nanobind. I have C++ code which calls nanobind::print and I want to test it. I tried to redirect the output of std::cout to a local std::ostringsteam, but when using nanobind::print I don't see any output content being added to the local ostringstream. How do I get the underlying rdbuf that nanobind::print uses? Any help is welcome.

The relevant piece of code is:

// Redirect std::cout
std::ostringstream local;
auto cout_buff = std::cout.rdbuf();
std::cout.rdbuf(local.rdbuf());

// This prints using nanobind::print
some_print_method();

// Restore std::cout
std::cout.rdbuf(cout_buff);

// Test that local buffer received something
std::string output = local.str();
REQUIRE( !output.empty() );

[hpkfft]

The nanobind function calls into Python to do the printing, and Python sends its output to the FILE* without using std::cout.
Maybe your testing tool has a way to capture stdout. For example, pytest can do that.