Let's try it out. First, if you're on Linux or OS X, install with the terminal command pip install cppimport.

Here's a simple C++ extension using pybind11:

<%
setup_pybind11(cfg)
%>
#include <pybind11/pybind11.h>

namespace py = pybind11;

int square(int x) {
    return x * x;
}

PYBIND11_PLUGIN(somecode) {
    pybind11::module m("somecode", "auto-compiled c++ extension");
    m.def("square", &square);
    return m.ptr();
}

Save this code as somecode.cpp.

Open a python interpreter and run these lines [1]:

>>> import cppimport
>>> somecode = cppimport.imp("somecode") #This will pause for a moment to compile the module
>>> somecode.square(9)
81

I'm a big fan of the workflow that this enables, where you can edit both C++ files and Python and recompilation happens transparently.

The technical description: cppimport looks for a C or C++ source file that matches the requested module. If such a file exists, the file is compiled as a Python extension using the options in a Mako header. The extension (shared library) that is produced is placed in the same folder as the C++ source file. Then, the extension is loaded.

Simpler language please: Sometimes Python just isn't fast enough. Or you have existing code in a C++ library. So, you write a Python extension module, a library of compiled code. I recommend pybind11 for C++ to Python bindings or cffi for C to Python bindings. I've done this a lot over the years. But, I discovered that my productivity goes through the floor when my development process goes from Edit -> Test in just Python to Edit -> Compile -> Test in Python plus C++. So, cppimport combines the process of compiling and importing an extension in Python so that you can type modulename = cppimport.imp("modulename") and not have to worry about multiple steps. Internally, when no matching Python module is found, cppimport looks for a file modulename.cpp. If one is found, it's compiled and loaded as an extension module.

[1]: The compilation should only happen the first time the module is imported. The C++ source is compared with a checksum on each import to determine if the file has changed. Included files are also incorporated into the checksum so recompilation happens automatically when a header file is edited.

[2]: Calling cppimport.set_quiet(False) will result in output that will be helpful in debugging compile errors. The default is to make the import process completely silent.

[3]: cppimport currently does not work on Windows. If you're on Windows and you really want cppimport, I'll happily accept a pull request.