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Chapter 6. Embedding

boost/python/exec.hpp

Introduction

Exposes a mechanism for embedding the python interpreter into C++ code.

Function eval

objecteval(strexpression,objectglobals=object(),objectlocals=object());

Effects

Evaluate Python expression from expression in the context specified by the dictionaries globals and locals.

Returns

An instance of object which holds the value of the expression.

Function exec

objectexec(strcode,objectglobals=object(),objectlocals=object());

Effects

Execute Python source code from code in the context specified by the dictionaries globals and locals.

Returns

An instance of object which holds the result of executing the code.

Function exec_file

objectexec\_file(strfilename,objectglobals=object(),objectlocals=object());

Effects

Execute Python source code from the file named by filename in the context specified by the dictionaries globals and locals.

Returns

An instance of object which holds the result of executing the code.

Examples

The following example demonstrates the use of import and exec to define a function in python, and later call it from within C++.

#include\<iostream\>#include\<string\>usingnamespaceboost::python;voidgreet(){// Retrieve the main module.objectmain=import("\_\_main\_\_");// Retrieve the main module's namespaceobjectglobal(main.attr("\_\_dict\_\_"));// Define greet function in Python.objectresult=exec("def greet(): \n"" return 'Hello from Python!' \n",global,global);// Create a reference to it.objectgreet=global["greet"];// Call it.std::stringmessage=extract\<std::string\>(greet());std::cout\<\<message\<\<std::endl;}

Instead of embedding the python script into a string, we could also store it in an a file...

defgreet():return'Hello from Python!'

... and execute that instead.

// ...// Load the greet function from a file.objectresult=exec\_file(script,global,global);// ...}

| | Copyright © 2002-2005, 2015 David Abrahams, Stefan Seefeld

Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt

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