Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

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Building Hello World

From Start To Finish

Now the first thing you'd want to do is to build the Hello World module and try it for yourself in Python. In this section, we shall outline the steps necessary to achieve that. We shall use the build tool that comes bundled with every boost distribution: bjam.

noteBuilding without bjam

Besides bjam, there are of course other ways to get your module built. What's written here should not be taken as "the one and only way". There are of course other build tools apart from bjam.

Take note however that the preferred build tool for Boost.Python is bjam. There are so many ways to set up the build incorrectly. Experience shows that 90% of the "I can't build Boost.Python" problems come from people who had to use a different tool.

We shall skip over the details. Our objective will be to simply create the hello world module and run it in Python. For a complete reference to building Boost.Python, check out: building.html. After this brief bjam tutorial, we should have built two DLLs:

if you are on Windows, and

if you are on Unix.

The tutorial example can be found in the directory: libs/python/example/tutorial. There, you can find:

The hello.cpp file is our C++ hello world example. The Jamfile is a minimalist bjam script that builds the DLLs for us.

Before anything else, you should have the bjam executable in your boost directory or somewhere in your path such that bjam can be executed in the command line. Pre-built Boost.Jam executables are available for most platforms. The complete list of Bjam executables can be found here.

Let's Jam!

jam

Here is our minimalist Jamfile:

# This is the top of our own project tree
project-root ;

import python ;

extension hello                     # Declare a Python extension called hello
:   hello.cpp                       # source
    # requirements and dependencies for Boost.Python extensions
    <template>@boost/libs/python/build/extension
    ;

First, we need to specify our location. You may place your project anywhere. project-root allows you to do that.

project-root ;

By doing so, you'll need a Jamrules file. Simply copy the one in the example/tutorial directory and tweak the path-global BOOST_ROOT to where your boost root directory is. The file has detailed instructions you can follow.

Then we will import the definitions needed by Python modules:

import python ;

Finally we declare our hello extension:

extension hello                     # Declare a Python extension called hello
:   hello.cpp                       # source

    # requirements and dependencies for Boost.Python extensions
    <template>@boost/libs/python/build/extension
    ;

The last part tells BJam that we are depending on the Boost Python Library.

Running bjam

bjam is run using your operating system's command line interpreter.

Start it up.

Make sure that the environment is set so that we can invoke the C++ compiler. With MSVC, that would mean running the Vcvars32.bat batch file. For instance:

C:\Program Files\Microsoft Visual Studio .NET 2003\Common7\Tools\vsvars32.bat

Some environment variables will have to be setup for proper building of our Python modules. Example:

set PYTHON_ROOT=c:/dev/tools/python
set PYTHON_VERSION=2.2

The above assumes that the Python installation is in c:/dev/tools/python and that we are using Python version 2.2. You'll have to tweak these appropriately.

tip Be sure not to include a third number, e.g. not "2.2.1", even if that's the version you have.

Take note that you may also do that through the Jamrules file we put in our project as detailed above. The file has detailed instructions you can follow.

Now we are ready... Be sure to cd to libs/python/example/tutorial where the tutorial "hello.cpp" and the "Jamfile" is situated.

Finally:

bjam -sTOOLS=vc-7_1

We are again assuming that we are using Microsoft Visual C++ version 7.1. If not, then you will have to specify the appropriate tool. See Building Boost Libraries for further details.

It should be building now:

cd C:\dev\boost\libs\python\example\tutorial
bjam -sTOOLS=msvc
...patience...
...found 1703 targets...
...updating 40 targets...

And so on... Finally:

Creating library bin\boost\libs\python\build\boost_python.dll\vc-7_1\debug\th
reading-multi\boost_python.lib and object bin\boost\libs\python\build\boost_pyth
on.dll\vc-7_1\debug\threading-multi\boost_python.exp
vc-C++ bin\tutorial\hello.pyd\vc-7_1\debug\threading-multi\hello.obj
hello.cpp
vc-Link bin\tutorial\hello.pyd\vc-7_1\debug\threading-multi\hello.pyd bin\tutori
al\hello.pyd\vc-7_1\debug\threading-multi\hello.lib
   Creating library bin\tutorial\hello.pyd\vc-7_1\debug\threading-multi\hello.li
b and object bin\tutorial\hello.pyd\vc-7_1\debug\threading-multi\hello.exp
...updated 31 targets...

If all is well, you should now have:

if you are on Windows, and

if you are on Unix.

boost_python.dll and hello.pyd can be found somewhere in your project's bin directory. After a successful build, you make it possible for the system to find boost_python.dll or libboost_python.so (usually done with LD_LIBRARY_PATH, DYLD_LIBRARY_PATH, or some other variable on *nix and with PATH on Windows) and for Python to find the hello module (Done with PYTHONPATH on all systems.)

You may now fire up Python and run our hello module:

>>> import hello
>>> print hello.greet()
hello, world

There you go... Have fun!

Copyright 2002-2005 Joel de Guzman, David Abrahams

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