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<H1><A NAME="SECTION007200000000000000000"></A><A NAME="lower-level-embedding"></A>
<BR>
5.2 Beyond Very High Level Embedding: An overview

</H1>

<P>
The high level interface gives you the ability to execute
arbitrary pieces of Python code from your application, but
exchanging data values is quite cumbersome to say the least. If
you want that, you should use lower level calls. At the cost of
having to write more C code, you can achieve almost anything.

<P>
It should be noted that extending Python and embedding Python
is quite the same activity, despite the different intent. Most
topics discussed in the previous chapters are still valid. To
show this, consider what the extension code from Python to C
really does:

<P>

<OL>
<LI>Convert data values from Python to C,
</LI>
<LI>Perform a function call to a C routine using the
        converted values, and
</LI>
<LI>Convert the data values from the call from C to Python.
</LI>
</OL>

<P>
When embedding Python, the interface code does:

<P>

<OL>
<LI>Convert data values from C to Python,
</LI>
<LI>Perform a function call to a Python interface routine
        using the converted values, and
</LI>
<LI>Convert the data values from the call from Python to C.
</LI>
</OL>

<P>
As you can see, the data conversion steps are simply swapped to
accommodate the different direction of the cross-language transfer.
The only difference is the routine that you call between both
data conversions. When extending, you call a C routine, when
embedding, you call a Python routine.

<P>
This chapter will not discuss how to convert data from Python
to C and vice versa.  Also, proper use of references and dealing
with errors is assumed to be understood.  Since these aspects do not
differ from extending the interpreter, you can refer to earlier
chapters for the required information.

<P>

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<span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span>
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