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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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	52
	53	<H1><A NAME="SECTION007200000000000000000"></A><A NAME="lower-level-embedding"></A>
	54	<BR>
	55	5.2 Beyond Very High Level Embedding: An overview
	56
	57	</H1>
	58
	59	<P>
	60	The high level interface gives you the ability to execute
	61	arbitrary pieces of Python code from your application, but
	62	exchanging data values is quite cumbersome to say the least. If
	63	you want that, you should use lower level calls. At the cost of
	64	having to write more C code, you can achieve almost anything.
65
66	<P>
67	It should be noted that extending Python and embedding Python
68	is quite the same activity, despite the different intent. Most
69	topics discussed in the previous chapters are still valid. To
70	show this, consider what the extension code from Python to C
71	really does:
72
73	<P>
74
75	<OL>
76	<LI>Convert data values from Python to C,
77	</LI>
78	<LI>Perform a function call to a C routine using the
79	converted values, and
80	</LI>
81	<LI>Convert the data values from the call from C to Python.
82	</LI>
83	</OL>
84
85	<P>
86	When embedding Python, the interface code does:
87
88	<P>
89
90	<OL>
91	<LI>Convert data values from C to Python,
92	</LI>
93	<LI>Perform a function call to a Python interface routine
94	using the converted values, and
95	</LI>
96	<LI>Convert the data values from the call from Python to C.
97	</LI>
98	</OL>
99
100	<P>
101	As you can see, the data conversion steps are simply swapped to
102	accommodate the different direction of the cross-language transfer.
103	The only difference is the routine that you call between both
104	data conversions. When extending, you call a C routine, when
105	embedding, you call a Python routine.
106
107	<P>
108	This chapter will not discuss how to convert data from Python
109	to C and vice versa. Also, proper use of references and dealing
110	with errors is assumed to be understood. Since these aspects do not
111	differ from extending the interpreter, you can refer to earlier
112	chapters for the required information.
113
114	<P>
115
116	<DIV CLASS="navigation">
117	<div class='online-navigation'>
118	<p></p><hr />
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123	border='0' height='32' alt='Previous Page' width='32' /></A></td>
124	<td class='online-navigation'><a rel="parent" title="5. Embedding Python in"
125	href="embedding.html"><img src='../icons/up.png'
126	border='0' height='32' alt='Up One Level' width='32' /></A></td>
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128	href="pure-embedding.html"><img src='../icons/next.png'
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133	border='0' height='32' alt='Contents' width='32' /></A></td>
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