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